ZXTape! 0Created with Ramsoft MakeTZXeh1 |$6:6:0: electronics help tape 1  G C E Tutoring  March 1985 !w(25,8):2000 r(10 ) t(5):9069m# Lscrhdr=9300T$:qsthdr=9350$:endsec=9400$:getans=9450$ fig2=8950":fig=9030F#:axes2=9000(#:eg=9040P#:axes=9100#:triangle=9150#:diagram=218:praise=9720% Dmoreq=9970&:coil=6000p:galv=6100:mag=62008 5br=8100:squrec=8850":squpar=8900" 4"Electronics help eh1"::"Energy and its sources" :" GCE Tutoring March 1985" 2u:"Hello, what's your name ?":m$:m$:"OK, ";m$;",":"I'll begin by telling you how touse this electronics tape." 4e:"This tape covers 4 subjects which all come under the headingof energy and power generation." :>:"Press the key marked C so I can type the next screenfull" <a$=:a$="c"62> = 60< >:z=1100d:z AF:"Thanks. From now on when I want you to press the C key, I'll say" D:" Hit C to continue" F4:"Here's the list of subjects on this program": Hm"energy and its sources power distribution transformers induction" K3:"Which subject do you want to try ? ":s$: Lc$=s$ N'(s$)>3s$=s$(13) Os$="ene"100d Ps$="pow"334N Qs$="tra" 300, Rs$="ind"200 Ss$="flu"500 Ts$="for"900 Us$="mot"600X _ 70F c d f i l n"Energy and its sources": pN"Energy can be broadly defined as'the ability or capacity to do work'. ": r"Energy can exist in a variety offorms, some more recogniseable as being capable of performing work than others. When energy isnot dependent on mechanical motion, the form is referred to as POTENTIAL ENERGY." sscrhdr t"Potential energy may be stored mechanically, such as in a spring or compressed gas. It canalso exist as chemical potentialenergy, which is released when two substances react chemically.Potential energy also exists in the nuclei of atoms." uscrhdr v"Kinetic energy is associated with mechanical motion. This canbe of a large moving object, or the individual movements of the molecules which make it up.": xD"Energy can be transformed back and forth from one state to another, while keeping the totalenergy (kinetic + potential) constant. An example of this is a swinging pendulum, in which all the energy is continuously changing from potential(at the top of the swing) to kinetic (at the bottom of the swing).": yscrhdr z"Conventional sources of energy involve the release of chemical potential energy, such as is availble from the combustion of coal or oil, or other fossil fuels.": |p"The chemical potential energy stored in coal varies between 15 and 30 million Joules per kilogram. Unfortunately, only about 40% of this energy is converted in power station to electrical energy. This makes the available energy around 10 million Joules per kilogram, which is the equivalent of about3 kilowatt hours (3 units) of electricity." }scrhdr ~"The energy released as heat froma chemical or nuclear reaction is used to produce steam at highpressure. This drives a turbine,which turns an electrical gener-ator. A typical power station has 10 generators, each providing about 100 megawatts of power.": "The heat at the core of a nuclear reactor is caused by theenergy released when the nuclei of the atomic fuel disintegrate.This process is called NUCLEAR FISSION .": scrhdr "Two fissionable fuels used in nuclear power stations are Uranium 235 and Plutonium 239. The energy available from these two fuels is roughly the same, and is about 100 million millionJoules, ie. about 5 million times more than in the same massof coal.": "Fossil fuels, such as coil and oil, and nuclear fuels are non- renewable. This means that once used, they cannot be replaced,soreserves are continuously deple-ted. Most alternative sources, however, are renewable.": scrhdr "Renewable energy sources includesolar energy, energy produced byharnessing the tides, and geo- thermal energy, which is heat from the earth's molten interior.": e"Geothermal energy can produce steam directly, which can drive a conventional turbine. Solar power can produce electricity directly, by using solar cells, though the efficiency is curren-tly too low for this to be econ-omically viable. Tidal power provides mechanical movement, which can drive a generator without the need for a turbine.": scrhdr qsthdr &"Roughly how much energy is stored as chemical potential energy in coal ? 1. between 15 and 30 thousand joules per kilogram 2. between 15 and 30 million joules per kilogram 3. none - it is kinetic energy": 4exp=2:egc=3:return=148:getans scrhdr "A nuclear reactor uses which fuel ? 1. plutonium 235 2. uranium 239 3. uranium 238 4. plutonium 239 5. plutonium 238": 4exp=4:egc=3:return=155:getans scrhdr "Nuclear fuels store much more energy than fossil fuels. How much more energy do they store ? 1. 1000 times more 2. 500 000 times more 3. over 1 000 000 times more": 4exp=3:egc=3:return=162:getans scrhdr @n$="energy sources":return=198:start=100d:endsec     induction  "Induction": ԟ"A changing magnetic field causes the flow of current in a coil by induction. The transformer relies on this effect for its operation.": "The changing magnetic field created by the AC applied to theprimary coil induces a current in the secondary. AC can therefore pass by mutual induction from one coil to another, but as DC does not produce a changing magnetic field, it cannot.": scrhdr @x=30:y=130:inv=1:coil:y=y-60<:coil ێ60<,20:0,110n:70F,20:0,110n:65A,20:0,110n:7,12 ;"The diagram shows":8,12 ;"inductive linking":9 ,12 ;"between two coils":19,0;" ":1,2;"The vertical lines represent an iron core. The curly lines represent the coils of wire.":19,0;" ":scrhdr |"Induction is improved by the addition of a magnetic material - eg. iron - into the path between the coils. " scrhdr qsthdr D"Which of these can pass from onecoil to another by induction :": V"1. AC 2. DC 3. both of these": 4exp=1:egc=3:return=240:getans scrhdr "Induction is greatly improved by introducing which of the following between two inducti- vely linked coils ? 1. iron 2. brass 3. either of these": 4exp=1:egc=3:return=248:getans scrhdr );n$="induction":return=298*:start=200:endsec * + , . 1transformers 4 6"Transformers": 8w"A transformer converts AC at onevoltage to AC at another. It consists of two coils linked by a soft iron core.": :J60<,62>:0,45-:65A,62>:0,45- ;,x=30:y=110n:inv=1:coil <-x=95_:y=110n:inv=-1:coil =Az=110 ::z::"A general formula follows.":scrhdr >"The ratio of voltage in to the voltage out depends on the number of turns in the input coil (the primary) to the numberof turns in the output coil (the secondary).": ?scrhdr @"The output voltage can be higherthan the input voltage by havingmore turns in the secondary thanthe primary. This is NOT gettingsomething for nothing - the current is proportionately less,so the power is the same.": Ascrhdr B"Alternatively, the output voltage can be less than the input by having less turns. Thiscan be useful, as mains electricity is at too high a voltage to operate electronic equipment.": Cscrhdr E"eg. a transformer has a primary coil with 1200 turns, and a secondary coil with 30 turns. What is the output voltage ?": F"The formula to use is :": Gb"Vout = Vin x (no. of turns on the secondary /no. of turns on the primary)": HT"Vout = Vin x 30/1200 = 240 x 30/1200 = 6 volts": Iscrhdr J"A transformer which raises the voltage is called a step-up transformer. When electricity is transmitted from a power station, it is at a very high voltage, sometimes as much as 400 000v. This is to reduce losses.": Kscrhdr L 350^ N"Power distribution"::"Electrical power distributed by the national grid is transmittedover long distances at one of three very high voltages (132Kv 275Kv or 400Kv). 1Kv is 1000v. This is much too high a voltage for industrial or domestic use, making it necessary to step the voltage down before the power can be used. To see why this apparently strange system is used, consider the following example.":scrhdr:"A generator produces 1 000 000W.If the power is transmitted at 1000v and the resistance of the pylon cable is 0.1 ohms, what power is lost ?": O" V = IR = I x 0.1 I = P/V = 1 000 000/1000 = 1000A V = 1000 x 0.1 =100v P = 100v x 1000A = 100 000W": Pscrhdr R"The generator is connected to a step up transformer before being connected to the pylon. Electricity is now transmitted at 100 000v. What is the new loss ?": T" V = IR = I x 0.1 I = P/V = 1 000 000/100 000 = 10A V = 10 x 0.1 = 1v P = 1v x 10A = 10W": V-"Which is 10 000 times less than before.": Wscrhdr Y"As well as less power lost in the line, the reduced current means that the pylon cables can be made from thinner wire, making them lighter and cheaper.": Zscrhdr:"There are many intermediate stages in reducing the voltage carried by pylons. For medium range distribution, 11Kv is used. This is supplied directly to heavy industry, but reduced further for lighter industrial use. Local sub-stations make the final reduction to 240v. This cannot be carried very far e.g. more than a kilometre or so, without uneconomic losses." [scrhdr \ ] 365m ^qsthdr `"A transformer with ";r(1)*120x;" turns on its primary has a secondary with ";r(2)*5;" turns. If the input voltage is 240v, what is the output ?": cKexp=10 *r(2)/r(1):egc=3:return=357e:getans emoreq hmore=1350^ j 395 mqsthdr n%actv=240*(r(1)+1) p"Assuming that power loss decreases with the square of voltage, how many times less power would a farmer lose if he supplied a distant barn with electricity at ";actv;"v instead of":"at 240v ?" r]egc=3:exp=r(1)*r(1)+2*r(1)+1:return=372t:getans tmoreq wmore=1365m |Dstart=334N:return=382~:n$="power distribution":endsec ~ ;start=300,:return=398:n$="K.E. and momentum" >n$="transformers":return=398:start=300,:endsec     galvanometers  "Galvanometers": "A galvanometer measures the flowof current. Unlike an ammeter, it reads zero at the centre. This means that it can display aflow of current in either direction.": Lx=30:y=75K:ptr=1:galv:x=130:ptr=-1:galv ::::::scrhdr "Inside a galvanometer there is asmall coil made of extremely fine wire. It is in the field ofa permanent magnet, so if current flows through it, the electromagnetic force produced either attracts or repels it.": "The coil is only free to rotate,so this is what it does. The movement of the coil is made more noticable by the addition of the pointer.": scrhdr qsthdr !"A galvanometer reads zero :": _"1. in the left had side 2. in the centre 3. on the right hand side": 4exp=2:egc=3:return=438:getans "A galvanometer measures": S"1. current 2. voltage 3. resistance": 4exp=1:egc=3:return=445:getans ?n$="galvanometers":return=498:start=400:endsec     flux patterns  "Flux patterns": o"A line whose direction at each point is that of the magnetic field is called a magnetic line of force.": 5"Lines of force can be plotted using a compass": scrhdr a"The lines of force from a bar magnet follow curves leading from one pole to the other.":  scrhdr  "A current flowing through a wirecreates a magnetic field,the lines of force of which radiate out in concentric circles from the wire.": scrhdr U?n$="flux patterns":return=598V:start=500:endsec V W X Z ]motors and dynamos ` b"Motors and dynamos": d^"An electric motor consists of a freely rotating coil of wire within a magnetic field.": hscrhdr j"Current flows through the brushes to the commutator, and then from the commutator to the coil. A magnetic field is created, causing the coil to be repelled from the magnet. This makes the armature, on which thecoil is mounted, rotate.": kscrhdr lJ"When the coil has rotated far enough, the current flows in theopposite direction through the coil. This is because the brushes now make contact with the opposite electrodes on the commutator to the ones before. Positive is now applied to the end of the coil which was previously negative, and vice versa." mscrhdr n"The magnetic field produced now repels the coil from the poles that it was previously attractedto. This causes another 1/2 turnof rotation.": qZ"The process then continues from the beginning, causing continuous rotation.": tscrhdr v"A dynamo generates electricity. Mechanically it is the same as an electric motor, but instead of current flowing through the coil causing rotation, the coil is rotated creating current to flow through it.": xscrhdr {qsthdr ~F"What changes the direction that current flows through the coil ?": V"1. the commutator 2. the brushes 3. none of these": 4exp=1:egc=3:return=645:getans 6"Electricity flows from the brushes to the :": O"1. commutator 2. permanent magnet 3. dynamo": 4exp=1:egc=3:return=652:getans O"A dynamo generates electricity when power is apllied in the form of :": k"1. passing current through the coil 2. rotating the armature 3. both" 4exp=2:egc=3:return=660:getans Dn$="motors and dynamos":return=698:start=600X:endsec       " ( z;start=600X:return=898:n$="matrix arithmetic" endsec     force, motion and current  "Force, motion and current": "When a magnetic field is appliedto a wire, a force is exerted at right angles to the field andthe current flowing through the wire. The direction of the forceis worked out using Fleming's left hand rule.": scrhdr "Fleming's left hand rule uses the fingers of left hand to represent the force, motion andcurrent. Force is on the thumb, direction of field is the fingerand current is the second finger": scrhdr A"A way to remember Fleming's lefthand rule is as follows :":: ["First Finger = field seCond finger = current thuMb = motion" scrhdr "Using Fleming's left hand rule, the direction of force in the example below can be worked out."::"The vertical arrows are the current, the arrow from left to right the field, and the other two arrows show the force." 14,7;">" %36$,59;:22,0 70F,45-:0,30:-4,-4:4,4:4,-4:80P,45-:-4,4:4,-4:4,4:-4,-4:0,30 90Z,65A:15,15:-3,0:3,0:0,-3:557,502:-15,-15:0,3:0,-3:3,0 ::: scrhdr:qsthdr d"Fleming's left hand rule uses the fingers of the left hand. The second finger represents :": N"1. motion 2. current 3. field": 4exp=2:egc=3:return=938:getans D"When a magnetic field is aplied to a wire, a force is exerted:": "1. at right angles to to the field 2. at right angles to the current 3. at right angles to both": 4exp=3:egc=3:return=945:getans Kn$="force, motion and current":return=998:start=900:endsec      N T    x z     @ B H   scalars and vectors  :"Scalars and vectors": }"Quantities such as mass, volume and length are called SCALAR quantities. Scalar quanties havesize but not direction.": z"Quantities such as velocity and acceleration have both size and direction. Thistype of quantity is called a vector.": D"The general propertyof a vector is that it has two components.": scrhdr qsthdr 1:"Which of these is a vector quantity ? " S:"1. length 2. time 3. velocity": 5exp=3:egc=3:return=1760:getans 3start=1700:return=1798:n$="vectors" endsec      vector arith. & laws  ":"Vector arithmetic and laws": ^"Vector arithmetic is very simpleand follows the laws of conventional arithmetic.": "Addition": <"Two vectors a and b add to make a vector c as follows:": ""a = 2 b = 3":" 1 4" 8i=12 :x=29:y=63?:br:x=93]:br &:"c = 2+3 = 5":" 1+4 = 5" x=101e:y=39':br  x=39':i=24:br !scrhdr $""a = 2 b = 3":" 1 4" &&:"c = 2+3 = 5":" 1+4 = 5" '9i=12 :x=29:y=151:br:x=93]:br (n:"Vector addition is commutative since it makes no difference which way round the vectors are added.": )&x=101e:y=39'+88X:br *x=39':i=24:br +"a + b = b + a = c": ."This is easy to see if you thinkof the vectors as position vectors. It makes no difference which one is taken first - the final position is the same." 0scrhdr 2"vector addition is also associative. Three vectors a, b and c add to make the same result in both of the following ways:": 54" d = a + (b + c) d = (a + b) + c" 8_:"Again, this can be easily understood if the vectors are thought of as positional." :3:"Vector subtraction is also conventional." <scrhdr ?"Vector multiplication": B/"A vector can be multiplied by a scalar:": D1" eg. a = 2 1": F:" eg. 2a = 2 x 2 = 4 2 x 1 = 2" GFi=12 :x=165:y=87W:br:x=77M:y=111o:br H(i=44,:x=85U:y=87W:br Iscrhdr Lqsthdr N/:"Is vector addition commutative ?":a$:a$ P;a$="No"a$="no""Yes it is ! Read the section again." Sa$="yes"a$="Yes"praise V(:"Is vector addition associative ?": X a$:a$ Z;a$="No"a$="no""Yes it is ! Read the section again." ]a$="yes"a$="Yes"praise b=n$="vector arithmetic":start=1800:return=1898j gendsec j k l n qvelocity triangles t v:"Velocity triangles"::"Sometimes it is necessary to know the length of a vector rather than its individual components.": x"Since the two components of a positional vector are at right angles to each other, the lengthof a vector can be calculated using Pythagoras' theorem." yscrhdr {:"For example, the length of a vector:"::" 4":" 3":::::::::"is 5. This can be seen in the triangle above." }1x=14-1:y=119w:i=12 :br ~label=0:triangle O"AB represent a the x component and BC the y component. AC is the length." scrhdr "The length of the vector can represent quantites such as speed. If an aircraft is flying at right angles to the wind its ground speed can be calculated using vectors:":  triangle q"AB represents the aircraft's airspeed, BC represents the wind velocity and AC represents the ground speed." 8,17;"air speed=150":10 ,17;"wind speed=80":12 ,17;"AC=150+80":12 +1,20;"AC=28900":14,21;"AC=170"  :::: scrhdr "Sometimes velocities will not be at right angles. In these cases Puthagorus cannot be used as the resultant triangle is not right angled." d:"The length can be calculated in these cases by drawing the triangle and measuring length." >n$="velocity triangles":start=1900l:return=1998 endsec   x$="": o=1̱x$ n=18 #w(o,n):x$(oo)+n-1,w(o,n) n o  H24,16,16,32 ,16,16,24,0 C24,8,8,4,8,8,24,0 F0,0,62>,64@,64@,64@,62>,0 E0,0,124|,2,2,2,124|,0 G0,66B,66B,66B,66B,66B,44,,0 G0,44,,66B,66B,66B,66B,66B,0  G0,0,60<,64@,124|,64@,60<,0 I240,8,120x,128,248,0,0,0 C0,0,0,4,126~,4,0,0 I248,136,136,136,0,0,0,0 C4,4,228,4,0,0,0,0 G240,8,240,8,240,0,0,0 G28,20,16,16,8,8,40(,568  E4,68D,228,68D,0,0,0,0 "G16,16,16,0,0,480,72H,480 %E12 ,18,18,12 ,0,0,0,0 (E7,4,4,8,8,144,80P,32 *G4,8,16,16,16,32 ,32 ,32 ,G32 ,32 ,32 ,16,16,16,8,4 /C32 ,16,8,8,8,4,4,4 2C4,4,4,8,8,8,16,32 4 )::(40(*3.14159Iρ/180)  z=31000 %v=((z^2-(z-1)^2)) u=v^0.5 C((u)-(u+0.5))<0.01z# =z;":";z-1;":";v^0.5 z  z=07 z:7-z 7x=13:"" c=110 :c x z 0::" G C E TUTORING"::" Orders"  p r ucoil (x,y,inv) x zKx,y:20*inv,0:z=15:0,-10 ,-*inv:z |-20*inv,0    galv (x,y,ptr)  x,y 20,0 35#,0,- -35#,0,-  x+557,y:20,0 3x+27,y+7:20,0,-/2 x+38&,y-7 ptr*7,12 7 8 : =mag @ Bx,y D%502,0:0,-15 G%-502,0:0,15  @"A geometric figure can be rotated by multiplying the individual coordinates by one ofthree different transformation matrices, depending on whether rotation through 90,180 or 270 is required.": B&"For a 90 rotation, multiply by:": E" 0 -1":" 1 0": H,"A 90 rotation is shoen in the diagram." I J:"The coordinates of the corners of the triangle are:": L&" 2 2 3":" 2 1 1": MM"which when multiplied by the matrix for a 90 rotation become:": N?" 0 -1 2 0-3 -3 1 0 3 2+0 2": O?" 0 -1 2 0-1 -1 1 0 1 2+0 2": P=" 0 -1 3 0-1 -1 1 0 1 3-0 3" R scrhdr:  Gx,y:0,16,-/3:x+i,y:0,16,/3: "There is a special matrix calledthe UNIT or identity matrix. If another matrix is multiplied by it there is no effect, rather like multiplying a number by 1 in ordinary arithmetic." $:"This is the 2x2 unit matrix:": " 1 0":" 0 1": 'x=8:i=24:y=80P:br scrhdr  " "square + rectangle "]27,568:502,0:0,502:-502,0:0,-502 "_27,568:100d,0:0,502:-100d,0:0,-502 "$7,2;"A D F" "%15,2;"B C E" " " "square + parallelogram "]27,568:75K,0:0,502:-75K,0:0,-502 "`27,568:75K,0:25,502:-75K,0:-25,-502 "#7,3;"A E D F" "!15,3;"B C" " " #K27,568:110n,0:568,41):0,557 #f15,7;"0":15,9 ;"2":15,11 ;"4":15,12 +1;"6" #E14,6;"0":12 ,6;"2":10 ,6;"4" #K27,568:110n,0:568,41):0,557 # [568+16,568+8:0,16:8,-16:-8,0 # ^568+32 ,568+16:0,32 :16,-32 :-16,0 #\568-10 ,568+16:-16,0:16,8:0,-8 #11 ,9 ;"A" #9 ,12 ;"B" #11 ,4;"C" #& #' #( #2K27,41):110n,0:27,41):0,557 #:]17,3;"0":17,6;"2":17,9 ;"4":17,12 ;"6" #<17,15;"8" #>\16,2;"0":14,2;"2":12 ,2;"4":10 ,2;"6" #A #Fi579+x,513+y:20,20:-20,20:-20,-20:20,-20: #Hc72H+x,568+y:0,30:-30,0:0,-30:30,0: #P'"Here is an example of ";n$ #R #Z #\ #_noises #b #d-z=120:0.01z# =,-24:z #f #h #i&z=15:0.3,t(z):z #l #mz=15:t(z):z: #n*7,9 ,5,-7,0 # # # #axes # #_30,90Z:210,0:30,90Z:0,557:0,-110n #10 ,2;"0" #f11 ,9 ;"90":11 ,15;"180":11 ,22;"270":11 ,29;"360" #atype=09124# #atype=19130# #.4,2;"1":16,1;"-1" #07,1;".5":13 ,0;"-.5" # #.7,2;"1":13 ,1;"-1" #.4,2;"2":16,1;"-2" # # # #draw triangle # #N30,60<:100d,0:0,60<:-100d,-60< #label=09175# #15,6;"adjacent" # 8,1;"hypoteneuse" #11 ,18;"opposite" #6123{,60<:0,7:7,0 #H41),60<:0,2:-3,2:-2,0 #14,2;"A" #14,17;"B" #6,17;"C" #::::::::: # # # #"Berk ! What's ";c$;" ?": #'"Wally ! ";c$;" isn't on the tape.": ##"Moron ! Try spelling straight": #"sorry, ";m$;" ? ": #"Are you tired, ";m$;" ?": #"Don't wind me up, ";m$: $T $V scrhdr() $Y $\9900&:: $ $ qsthdr() $ $'9600%:9900&:egc=0: $ $ $endsec(start,n$) $ $5"That finishes ";n$:"Hit r to repeat this section" $ 9900& $a$="r"start $return $ $ $getans(loop,exp) $ $?dp=0:err=0:u$:u$:(u$)>10 err=1 $(u$)=09460$ $[j=1̱(u$):(u$(jj))<45-ů(u$(jj))>579ů(u$(jj))=47/err=1 $%9480%:j:u$="-."err=1 $Cerr=1dp>1"type the answer as a number":9460$ $=ans=(u$):(exp-ans)>0.005y# ="No, the answer is ";exp $$(ans-exp)0.005y# =9720% $return $ % %$(u$(jj))=46.dp=dp+1 % ,j>1Ư(u$(jj))=45-err=1 %  %k9800H&:d1=r(1)/10 +r(2)/100d+r(3)/1000:dec=d1:int=1000*dec %& %A"See if you understand this by trying the following examples" % 9800H& % %"True or false ?" %a$ %a$ %a$"t"a$"f"9650% % %n:n;"/";:d:d: % 9630% %h"No. Don't add the numbers together. It's just the second number, so the answer is ";r(2) % %K"No, its the second number, not the first, so the answer is ";r(2) % %%9720%+((*9 )+1): % "Good": % "Correct": %"Right again": %"OK": %"That's it": %"Brilliant !": %"Well done": &"Very good": &"Genius !": &HWz=110 :r(z)=(*9 )+1:z:r(1)r(2)9800H&: &R#r(1)r(2)9800H& &\ &z "trap": & &"Hit C to continue" &a$= &a$="c"9950& &a$="r"9950& &a$="q"9950& & 9920& & &z=1502:z & &more=0 &"More questions ?": & d$:d$ &d$=d$(11) &d$="y"more=1 &  >@@@>||BBBBB,,BBBBB<@|@<x~(8DD0H0  P    X 5  32&crhdT$sthd$ndse$etan$ig"iF#xes(#P#xe#riangl#iagrarais%ore&oipala8qure"qupa"MNickgxetur*r$ntarctorxyFnDnU3N inductionAcSC6eh2 ĆYAƆ-k(3,550&):j$(3,550&) electronics help tape 2  GCE Tutoring 6:6:0: !w(25,8):2000 r(10 ) t(5):9069m# ]galv=9995 ':scrhdr=9300T$:qsthdr=9350$:endsec=9400$:getans=9450$ fig2=8950":fig=9030F#:axes2=9000(#:eg=9040P#:axes=9100#:triangle=9150#:diagram=218:praise=9720% moreq=9980& electroscope=7400:parallel=7350:inc=0:triode=7700:diode=7600:series=7300:link=7250R:wiring=7000X:bulb=7050:resistor=7100:meter=7150:battery=7200  5br=8100:squrec=8850":squpar=8900" /"Electronics help eh2"::"Measuring devices" :" GCE Tutoring March 1985" 2u:"Hello, what's your name ?":n$:n$:"OK, ";n$;",":"I'll begin by telling you how touse this electronics tape." 4[:"This program covers 5 subjects which all come under the headingof measuring devices." :>:"Press the key marked C so I can type the next screenfull" <a$=:a$="c"62> = 60< >:z=1100d:z AF:"Thanks. From now on when I want you to press the C key, I'll say" D:" Hit C to continue" F4:"Here's the list of subjects on this program": H"ammeters voltmeters galvanometers cathode ray tubes oscilloscopes" K2:"Which subject do you want to try ?":s$: Lc$=s$ N'(s$)>3s$=s$(13) Os$="gal"100d Rs$="amm"400 Ss$="cat"500 Us$="osc"500 Vs$="vol"400 _ 70F c d f i l n"Galvanometers": p"A galvanometer measures the flowof current. Unlike an ammeter, reads zero at the centre. This means that it can display a flowof current in either direction.": rQ"A circuit with a resistor and battery is shown on the next page.":scrhdr sdgnum=2:3500 tscrhdr v"Inside a galvanometer there is asmall coil of extremely fine wire. It is in the field of a permanent magnet, so if current flows through it, the electro- magnetic force either attracts or repels it.": x"The coil is only free to rotate,so this is what it does. The movement is made more noticeableby the addition of the pointer.": }scrhdr qsthdr "A galvanometer reads zero:": _"1. at the left hand side 2. at the centre 3. at the right hand side": 4exp=2:egc=3:return=138:getans "A galvanometer measures:": S"1. current 2. voltage 3. resistance": 4exp=1:egc=3:return=145:getans 2n$=c$:start=100d:return=198:endsec     Ohm's law  "Ohm's law": ԗ"The flow of current around a circuit is impeded by the resistance of conductors in its path. This resistance is measured in ohms.": "The higher the voltage pushing the current through a circuit, the greater the current that canflow. This is analogous to a plumbing system with narrow tubes - the greater the water pressure, the larger the flow ofwater.": scrhdr u"Voltage, current and resistance are connected by a relationship known as Ohm's law. The equations are :": "V=IR R=V/I I=V/R": N"An easy way of remembering theseformulae is by learning this diagram:": scrhdr:7550~ scrhdr `"Place your finger over the unknown quantity, and the equation required is left.": 2scrhdr:7550~:" V=IR I=V/R R=V/I" scrhdr e"eg. what current flows through a resistance of 15 ohms if the battery voltage is 3v ?": L"I=V/R =3/15 =0.2A": scrhdr qsthdr "Ohm's law states that :": T"1. V=I/R 2. V=R/I 3. V=IR ?": 4exp=3:egc=3:return=252:getans "What current flows through a resistance of ";r(1)*10 ;" Ohms if the":"voltage across it is ";r(2);" volts ?": &exp=r(2)/(r(1)*10 ) 'egc=3:return=260:getans )2n$=c$:start=200:return=298*:endsec * + . 1series and parallel 4 6"Series and parallel": 8"Two bulbs can be wired in two different ways. If they are wired one after the other, it iscalled SERIES. This is shown below:": ;'scrhdr:wiring:battery:link:series <scrhdr >"As there is 12v across both bulbs, and the bulbs have the same resistance as each other, half the voltage is dropped across one bulb, and half acrossthe other. The current is therefore 1A.": ?scrhdr @o"The alternative wiring arrangement is to have the bulbsside by side. This is known as parallel.": B)scrhdr:wiring:battery:bulb:parallel Clink:scrhdr E^"12v is across both bulbs. The current through each is 1A, so the total current is 2A.": Fscrhdr H?"The different wiring arrangements have theit own advantages and disadvantages. An example of series wiring is Xmas tree lights. Each bulb is 12v, but 20 in series will run at 12v x 20 = 240v, which is mains voltage. Unfortunately, ifone blows, all the lights go outas the circuit is broken.": J"A parallel wiring arrangement has the advantage that if one bulb blows, the others stay on. House hold lighting is wired this way.": Kscrhdr L"Resistors in series add:": O"total R = R1 + R2": R2"Resistors in parallel are more complicated:": T "total R = 1/( 1/R1 + 1/R2)": ^qsthdr `f"Two bulbs designed for American mains (110v) are to be run off 220v. How should they be wired ?": cu"1. series 2. parallel 3. one in series and one in parallel ?": f4exp=1:egc=3:return=360h:getans h"If a resistor of ";r(1);" ohms ":"and another of ";r(2);" ohms":"are wired in series, what is the total resistance ?": jBexp=r(1)+r(2):egc=3:return=365m:getans m"If a resistor of ";r(1);" ohms ":"and another of ";r(2);" ohms ":"are wired in parallel, what is the total resistance ?": p\exp=1/(1/r(1)+1/r(2)):egc=3:return=370r:getans 2n$=c$:start=300,:return=398:endsec     ammeters and voltmeters s$="vol""Voltmeters": s$="amm""Ammeters": s$="amm""An ammeter is a device which measures the current flow through a circuit. As it measures the flow, a break must be made in the circuit, and the ammeter connected in this break.": s$="amm"scrhdr:battery:wiring:t$="A":meter:bulb:12 ,7;"battery":10 ,14;"bulb":7,11 ;"ammeter":19,0;" " s$="amm"scrhdr s$="amm"420  "A voltmeter is a device which measures the voltage ACROSS a device in a circuit. Because voltage is not analogous with flow, it DOES NOT measure the voltage through a device. What flows through a device is current, which is measured in amps.":  9250"$ scrhdr "An ammeter can be used as a voltmeter by using the principles involved in Ohm's law. If a resistor is connected in series with the ammeter, the current flowing through it is proportional to the voltage pushing it.": "eg. If an ammeter that reads 0 to 1A is connected in series with a 10 ohm resistor, 10 volts will be required to cause a flow of 1A, and therefore make a full scale reading.": scrhdr "eg. An ammeter which reads 0 to 1mA (0.001A) is required to read 0 to 300v. What resistor is needed in series": c"V=300v I=0.001 R=V/I =300/0.001 =300 000 ohms": scrhdr qsthdr "An ammeter that reads 0 to ";r(1);" mA is required to read 0 to ";r(2);" volts":"What resistor needs to be placed in series ?": Mexp=1000*r(2)/r(1):egc=3:return=440:getans moreq more=1432 scrhdr s$="amm""An ammeter measures current : 1. flowing through a circuit 2. across components 3. both 1. and 2." >s$="amm"egc=3:exp=1:return=452:getans Ŀs$="vol""An voltmeter measures voltage : 1. flowing through a circuit 2. across components 3. both 1. and 2." >s$="vol"egc=3:exp=2:return=458:getans 2n$=c$:start=400:return=498:endsec     CRO   c$="osc""Oscilloscopes": c$="osc""A cathode ray oscilloscope is anelectronic instrument which produces a graph of voltage against time on the equivalent of a small TV screen.": Tc$="osc""The picture is produced on a cathode ray tube."::scrhdr:522  "The cathode ray tube"::"This is fragile electronic device which has a fluorescent screen at one end and an electron gun at the otherwhich causes the screen to fluoresce.": scrhdr "The beam is moved by applying a high voltage to flat electrodes called plates. The plates deflect the beam horizontally or vertically by attracting or repelling it.": "A diagram of a CRT is shown on the next page."::scrhdr:dgnum=3:3500 :3,15;"Y plates";18,14;"fluorescent screen":scrhdr  #n$="cathode ray tubes":532  "The graph is produced by scanning the beam across the screen. This is achieved by applying a sawtooth waveform to the X plates,which move the beam horizontally.": scrhdr y"This tracks the beam across the screen, and then very quickly returns to the left hand side for the next sweep.": scrhdr:"A graph of voltage against time for a sawtooth waveform is shownon the next page.":scrhdr:dgnum=1:3500 :scrhdr v"The voltage being measured is amplified and then applied to the Y plates, which move the beam vertically.": scrhdr qsthdr Z"What does a cathode ray tube accelerate that strikes the fluorescent screen ?": U"1. electrons 2. alpha particles 3. cathodes ?": 4exp=1:egc=3:return=545!:getans !U"Which electrode produces vertical movement of the electron beam ?": $N"1. Y plates 2. X plates 3. anode": &4exp=1:egc=3:return=552(:getans (scrhdr +s$="osc""An oscilloscope uses a certain type of waveform to drive the X-plates. Is it : 1. sawtooth 2. trianglar 3. a sine wave": .>s$="osc"exp=1:egc=3:return=5600:getans U2start=500:return=598V:n$=c$:endsec V W X Z `       " (       N T    x z     @ B H        k l n t  x$="": o=1̱x$ n=18 #w(o,n):x$(oo)+n-1,w(o,n) n o  H24,16,16,32 ,16,16,24,0 C24,8,8,4,8,8,24,0 F0,0,62>,64@,64@,64@,62>,0 E0,0,124|,2,2,2,124|,0 G0,66B,66B,66B,66B,66B,44,,0 G0,44,,66B,66B,66B,66B,66B,0  G0,0,60<,64@,124|,64@,60<,0 I240,8,120x,128,248,0,0,0 C0,0,0,4,126~,4,0,0 I248,136,136,136,0,0,0,0 C4,4,228,4,0,0,0,0 G240,8,240,8,240,0,0,0 G28,20,16,16,8,8,40(,568  E4,68D,228,68D,0,0,0,0 "G16,16,16,0,0,480,72H,480 %E12 ,18,18,12 ,0,0,0,0 (E7,4,4,8,8,144,80P,32 *G4,8,16,16,16,32 ,32 ,32 ,G32 ,32 ,32 ,16,16,16,8,4 /C32 ,16,8,8,8,4,4,4 2C4,4,4,8,8,8,16,32 4   save screen ptr2=0 z=16384@23296[ ptr=z-16383? data=z Jdata0ptr2=ptr2+1:j$(dgnum,ptr2)=(data):k(dgnum,ptr2)=z z    !fetch screen $ &z=16384@23296[ (ptr=z-16383? fetch screen bits  z=1550& k(dgnum,z),(j$(dgnum,z)) z   z=31000 %v=((z^2-(z-1)^2)) u=v^0.5 C((u)-(u+0.5))<0.01z# =z;":";z-1;":";v^0.5 z  z=07 z:7-z 7x=13:"" c=110 :c x z 0::" G C E TUTORING"::" Orders"  z=025 x=14 code=(c$(xx))+z  code>"z"code=code-26 code; x::z ( X Z ]wiring ` b502,110n:0,40(:40(,0:130,150:40(,0:0,-40(:170,70F:0,-40(:-120x,0:0,40( g   bulb  170+inc,110n z=15 0,-8, z !170+inc,90Z,20     resistor  170,110n z=14 %5,-5:-5,-5 z     meter(type)  110n,150,20 3,14-1;t$ 17,0;" "    " % battery ( *502,110n ,0,-18 /8-10 ,0:20,0:-10 ,0 2502,83S 48-15,0:30,0:-15,0 60,-18 P R T Wlink Z \&90Z,150:40(,0 |   bulbs in series  '170,96`:0,-12 170,103g,7 170,77M,7 170,111o x=14 & 2,-2:-2,-2 x 170,111o-26 x=14 & 2,-2:-2,-2 x     parallel  inc=45-:bulb 9170+inc,70F:0,-40(:-inc,0 9170+inc,110n:0,40(:-inc,0  inc=0    electroscope  502,502 $502,0:0,502 &-502,0:0,-502 75K,115s 0,-45- /75K,115s-37%:4,-7 &60<,115s:30,0  V$7000X:7050:7150 X'170,150:0,40( | ~  triangle VIR  80P,80P <100d,0:-502,86V:-502,-86V 130,80P 70,43+:-25,0:502,0 9 ,12 +1;"I" '9 ,12 +1+5;"R" 4,12 +4;"V" 15,0;" "    diode  502,502 '0,80P:30,0,- 0,-80P -30,0,- 65A,145 %0,-10 :-7,0 14,0 524,43+ x=14 6,0,- x 524,43+ 0,-10 524+24,43+ 0,-10 4,11 ;"Anode" 17,11 ;"Cathode"    triode  "10 ,6;"- - - Grid"  diode D F H Kradio N P502,80P RJ502,0:0,502:-502,0:0,-502 U110n,80P XJ502,0:0,502:-502,0:0,-502 Z170,80P \J502,0:0,502:-502,0:0,-502 v  " "square + rectangle "]27,568:502,0:0,502:-502,0:0,-502 "_27,568:100d,0:0,502:-100d,0:0,-502 "$7,2;"A D F" "%15,2;"B C E" " " "square + parallelogram "]27,568:75K,0:0,502:-75K,0:0,-502 "`27,568:75K,0:25,502:-75K,0:-25,-502 "#7,3;"A E D F" "!15,3;"B C" " " #K27,568:110n,0:568,41):0,557 #f15,7;"0":15,9 ;"2":15,11 ;"4":15,12 +1;"6" #E14,6;"0":12 ,6;"2":10 ,6;"4" #K27,568:110n,0:568,41):0,557 # [568+16,568+8:0,16:8,-16:-8,0 # ^568+32 ,568+16:0,32 :16,-32 :-16,0 #\568-10 ,568+16:-16,0:16,8:0,-8 #11 ,9 ;"A" #9 ,12 ;"B" #11 ,4;"C" #& #' #( #2K27,41):110n,0:27,41):0,557 #:]17,3;"0":17,6;"2":17,9 ;"4":17,12 ;"6" #<17,15;"8" #>\16,2;"0":14,2;"2":12 ,2;"4":10 ,2;"6" #A #Fi579+x,513+y:20,20:-20,20:-20,-20:20,-20: #Hc72H+x,568+y:0,30:-30,0:0,-30:30,0: #P'"Here is an example of ";n$ #R #Z #\ #_noises #b #d-z=120:0.01z# =,-24:z #f #h #i&z=15:0.3,t(z):z #l #mz=15:t(z):z: #n*7,9 ,5,-7,0 # # # #axes # #_30,90Z:210,0:30,90Z:0,557:0,-110n #10 ,2;"0" #f11 ,9 ;"90":11 ,15;"180":11 ,22;"270":11 ,29;"360" #atype=09124# #atype=19130# #.4,2;"1":16,1;"-1" #07,1;".5":13 ,0;"-.5" # #.7,2;"1":13 ,1;"-1" #.4,2;"2":16,1;"-2" # # # # # # # #"Berk ! What's ";c$;" ?": #'"Wally ! ";c$;" isn't on the tape.": ##"Moron ! Try spelling straight": #"sorry, ";n$;" ? ": #"Are you tired, ";n$;" ?": #"Don't wind me up, ";n$: $" voltmeter $$scrhdr:battery:wiring:t$="":bulb:12 ,7;"battery":10 ,14;"":7,11 ;"":19,0;" " $'O230,90Z,20:10 ,28;"V";10 ,14;"bulb" $)&90Z,150:40(,0 $*v230,70F:0,-40(:-120x,0:230,110n:0,40(:-120x,0 $+19,0;" " $, $T $V scrhdr() $Y $\9900&:: $ $ qsthdr() $ $'9600%:9900&:egc=0: $ $ $endsec(start,n$) $ $7"That finishes: ":n$:"Hit r to repeat this section" $ 9900& $a$="r"start $return $ $ $getans(loop,exp) $ $?dp=0:err=0:u$:u$:(u$)>10 err=1 $(u$)=09460$ $[j=1̱(u$):(u$(jj))<45-ů(u$(jj))>579ů(u$(jj))=47/err=1 $%9480%:j:u$="-."err=1 $Cerr=1dp>1"type the answer as a number":9460$ $=ans=(u$):(exp-ans)>0.005y# ="No, the answer is ";exp $$(ans-exp)0.005y# =9720% $return $ % %$(u$(jj))=46.dp=dp+1 % ,j>1Ư(u$(jj))=45-err=1 %  %k9800H&:d1=r(1)/10 +r(2)/100d+r(3)/1000:dec=d1:int=1000*dec %& %A"See if you understand this by trying the following examples" % 9800H& % %"True or false ?" %a$ %a$ %a$"t"a$"f"9650% % %n:n;"/";:d:d: % 9630% %h"No. Don't add the numbers together. It's just the second number, so the answer is ";r(2) % %K"No, its the second number, not the first, so the answer is ";r(2) % %%9720%+((*9 )+1): % "Good": % "Correct": %"Right again": %"OK": %"That's it": %"Brilliant !": %"Well done": &"Very good": &"Genius !": &HWz=110 :r(z)=(*9 )+1:z:r(1)r(2)9800H&: &R#r(1)r(2)9800H& &\ &z "trap": & &"Hit C to continue" &a$= &a$="c"9950& &a$="r"9950& & 9920& & &z=1502:z & &Rmore=0:"More questions of this type? (y or n)":e$:e$=""9980& &?e$(11)="y"e$(11)="Y"more=1 & ' ' galvanometer ' ? &@@@@@@@@AAAAAAAAAAAiBBBBBBBBBBBBBhCiCCCCCCCCCCCCCChDiDDDDDDDDDDDDDDiEEEEEEEEEEEEEEiFFFFFFFFFFFFFFiGGGGGGGGGGGGG H HHHH)H+H.H1H4HIHJHNHOHTHUHiHvH I IIII)I+I.I0I4IIIJINIOITIUIiIjIkIlImInIoIpIqIrIsItIuIvIwIII J JJJJ)J+J.J0J4J6JIJJJNJOJTJUJvJJJJ K KKKK)K+K.K0K4K6KIKJKNKOKTKUKvKKKKK L LLLL)L+L.L0L4L6LILNLOLTLvLLLLL M MMMM)M*M.M0M4M5MIMNMOMTMVMMMMM N NNNN)N*N.N0N4N5NINNNONTNVNNNNN O OOOO)O*O.O0O4O5OIOVOXXXXXXXXX X X X X XXXXXXXXXXXXXXXXXXX X!X"X#X$X%X&X'X(X)X*X+X,X-X.X/X0X1X2X3X4X5X6X7X8X9X:X;XX?X@XAXBXCXDXEXFXGXHXIXJXKXLXMXNXOXPXQXRXSXTXUXVXWXXXYXZX[X\X]X^X_X`XaXbXcXdXeXfXgXhXiXjXkXlXmXnXoXpXqXrXsXtXuXvXwXxXyXzX{X|X}X~XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXYYYYYYYYY Y Y Y Y YYYYYYYYYYY@@@@@@AAAAAAAABBBBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFFFGGGGGGGGGGGGGG HHHHH*H0H2H3H6HJHVHjHvHwHHHHHHHHHH IIIII*I0I1I3I6IJIVIjIvIwIIIIIIIIIIIII JJJJJ*J0J1J3J6JJJVJjJvJwJJJJJJJJJJJJJJJJJ KKKKK*K0K2K6KJKVKjKvKwKKKKKKKKKKKKKKKKK LLLLL*L0L1L2L6LJLVLjLvLwLLLLLLLLLLLLLLLLLLLLL MMMMM*M1M2M6MJMVMjMvMwMMMMMMMMMMMMMMMMMMMM NNNNN*N1N2N6NJNVNjNvNwNNNNNNNNNNNNNNNNN OOOOO*O6OJOVOWOjOvOwOOOOOOOOOOO PP*P6P QQ*Q6Q RR*R6R SS*S+S,S-S.S/S0S1S2S3S4S5S6S TT UU VV WWXXXXXXXXX X X X X XXXXXXXXXXXXXXXXXXX X!X"X#X$X%X&X'X(X)X*X+X,X-X.X/X0X1X2X3X4X5X6X7X8X9X:X;XX?X@XAXBXCXDXEXFXGXHXIXJXKXLXMXNXOXPXQXRXSXTXUXVXWXXXYXZX[X\X]X^X_X`XaXbXcXdXeXfXgXhXiXjXkXlXmXnXoXpXqXrXsXtXuXvXwXxXyXzX{X|X}X~XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX@@AAABBBBBBBBCCCCCCCCDDDDDDDDEEEEEEEEEFFFFFFFFFGGGGG H HH)H-H1H4HIHTHUHiHoHrHsHtHuHHHHHHHHHHHHHHHHHHHH I II)I-I.I1I4IIIOIPIQIRISIUIiIjIoIrIsItIuIyIzI|IIIIIIIIIIIIIII J J JJ)J.J1J4JIJUJiJjJoJrJsJtJuJwJxJyJzJ{J|J}JJJJJJJJJJJJJJJJJJJJJJ K KKK)K.K1K4KIKUKiKjKoKrKsKtKuKwKxKyKzK{K|K}KKKKKKKKKKKKKKKKKKKKK L L LLL)L.L/L0L1L2L3L4L5LILOLPLQLRLSLULiLjLoLrLsLtLuLwLxLyLzL{L|L}LLLLLLLLLLLLLLLLLLLL M MMM)M1M4M5MIMOMRMSMTMUMVMiMjMoMrMsMtMuMwMxMyMzM{M|M}MMMMMMMMMMMMMMMMMMMM N NNN)N1N4N5NINONRNSNTNUNiNjNoNpNqNrNsNtNuNvNwNxNyNzN{N|N}NNNNNNNNNNNNNNNNNN O O OOO)O4O5OIOOOROSOTOUOiOjOoOuOOOOOOOOOOOO P-P Q-Q R-R S-S T U V WXXXXXXXXX X X X X XXXXXXXXXXXXXXXXXXX X!X"X#X$X%X&X'X(X)X*X+X,X-X.X/X0X1X2X3X4X5X6X7X8X9X:X;XX?X@XAXBXCXDXEXFXGXHXIXJXKXLXMXNXOXPXQXRXSXTXUXVXWXXXYXZX[X\X]X^X_X`XaXbXcXdXeXfXgXhXiXjXkXlXmXnXoXpXqXrXsXtXuXvXwXxXyXzX{X|X}X~XXXXXXXXXXXXXXXXXXw&    `D ( @D H $(  "(  @         0    ?   @8h8  @ 0TD @ !0 Tx  "@ T@  `$ 8T< ` (0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 ?`@<8D8x8h888CDDDDTDD D<(:"Press the key marked C so I can type the next screenfull" <a$=:a$="c"62> = 60< >:z=120:z AF:"Thanks. From now on when I want you to press the C key, I'll say" D:" Hit C to continue" F4:"Here's the list of subjects on this program": H"circuits ohm's law series and parallel electromotive force current power" K2:"Which subject do you want to try ?":s$: Lc$=s$ N'(s$)>3s$=s$(13) Os$="cir"100d Ps$="ohm"200 Qs$="ser" 300, Rs$="ele"400 Ss$="cur"500 Ts$="pow"600X _ 70F c d f i circuits l n"Circuits": p~"An electric circuit allows the flow of current from its source and back again. This is why it is called a ""circuit"".": rQ"A circuit with a bulb and battery is shown on the next page.":scrhdr siwiring:battery:link:bulb:12 ,8;"battery";7,15;"bulb";19,0;" " tscrhdr v"Circuits are drawn ""schematically"". This means thatsymbols are used for components in the circuit instead of pictures. The circuit on the previous page is drawn with these symbols.": wscrhdr xD"If the two terminals (+ve and -ve) of a battery are connected together without going through a bulb or any other component, a short circuit is formed. This draws a very large current from the battery. In the case of mains electricity the wire wouldbecome very hot due to the largecurrent, and might catch fire.": zscrhdr }qsthdr 2n$=c$:start=100d:return=198:endsec     Ohm's law  "Ohm's law": ԗ"The flow of current around a circuit is impeded by the resistance of conductors in its path. This resistance is measured in ohms.": "The higher the voltage pushing the current through a circuit, the greater the current that canflow. This is analogous to a plumbing system with narrow tubes - the greater the water pressure, the larger the flow ofwater.": scrhdr u"Voltage, current and resistance are connected by a relationship known as Ohm's law. The equations are :": "V=IR R=V/I I=V/R": E"In the formulae, V is voltage, Iis current and R is resistance.": N"An easy way of remembering theseformulae is by learning this diagram:": scrhdr:7550~ scrhdr `"Place your finger over the unknown quantity, and the equation required is left.": 2scrhdr:7550~:" V=IR I=V/R R=V/I" scrhdr e"eg. what current flows through a resistance of 15 ohms if the battery voltage is 3v ?": L"I=V/R =3/15 =0.2A": scrhdr qsthdr "Ohm's law states that :": T"1. V=I/R 2. V=R/I 3. V=IR ?":  4exp=3:egc=3:return=251:getans  "What current flows through a resistance of ";r(1)*10 ;" Ohms if the":"voltage across it is ";r(2);" volts ?": &exp=r(2)/(r(1)*10 ) 'egc=3:return=260:getans  9990' t$="y"qsthdr:252 )2n$=c$:start=200:return=298*:endsec * + . 1series and parallel 4 6"Series and parallel": 8"Two bulbs can be wired in two different ways. If they are wired one after the other, it iscalled SERIES. This is shown below:": ;tscrhdr:wiring:battery:link:series:12 ,8;"battery";7,15;"bulbs";19,0;" " <scrhdr >"As there is 12v across both bulbs, and the bulbs have the same resistance as each other, half the voltage is dropped across one bulb, and half acrossthe other. The current is therefore 1A.": ?scrhdr @o"The alternative wiring arrangement is to have the bulbsside by side. This is known as parallel.": Bscrhdr:wiring:battery:bulb:parallel:12 ,8;"battery";7,16;"bulb";7,22;"bulb";19,0;" " Clink:scrhdr E^"12v is across both bulbs. The current through each is 1A, so the total current is 2A.": Fscrhdr H?"The different wiring arrangements have their own advantages and disadvantages. An example of series wiring is Xmas tree lights. Each bulb is 12v, but 20 in series will run at 12v x 20 = 240v, which is mains voltage. Unfortunately, ifone blows, all the lights go outas the circuit is broken.": J"A parallel wiring arrangement has the advantage that if one bulb blows, the others stay on. House hold lighting is wired this way.": Kscrhdr L"Resistors in series add:": O"total R = R1 + R2": Pscrhdr R2"Resistors in parallel are more complicated:": T "total R = 1/( 1/R1 + 1/R2)": V"This formula needs explaining. A good way of understanding it is to think in terms of conduct-ance (the reciprocal of resista-nce). ": W"conductance = 1/resistance So the formula for parallel resistance really involves adding conductances.":scrhdr X"In an analogous plumbing system,two pipes side by side representtwo resistors in parallel. They allow twice the flow that one pipe permits. In other words, there is only half the original resistance to flow." [ ^qsthdr `f"Two bulbs designed for American mains (110v) are to be run off 220v. How should they be wired ?": cu"1. series 2. parallel 3. one in series and one in parallel ?": f4exp=1:egc=3:return=360h:getans h"If a resistor of ";r(1);" ohms ":"and another of ";r(2);" ohms":"are wired in series, what is the total resistance ?": jBexp=r(1)+r(2):egc=3:return=365m:getans m"If a resistor of ";r(1);" ohms ":"and another of ";r(2);" ohms ":"are wired in parallel, what is the total resistance ?": p\exp=1/(1/r(1)+1/r(2)):egc=3:return=370r:getans 2n$=c$:start=300,:return=398:endsec     emf  "Electromotive force": "The electrical potential difference between the terminalsof any device is also known as electromotive force, or EMF for short.": "EMF can be thought of as the 'pressure' forcing the flow of electricity. EMF is measured in volts, anything under 50v being regarded as low." scrhdr "When current flows from a device, the potential differencedrops slightly. The strict definition of EMF, therefore, isthe potential difference when the current flowing is zero. This condition is called 'open circuit' or 'no load'.": scrhdr "When a potential source of electrical energy, such as an inductor or capacitor, receives energy from the rest of the circuit in which it is used, it develops counter EMF.": scrhdr "Counter EMF is produced by a running electric motor, due to its generator-like nature. The total EMF is the EMF supplied tothe motor minus the counter EMF.Counter EMF is also known as back EMF.": scrhdr:525  qsthdr scrhdr 6"What are the units that current is measured in ?": Q"1. amps 2. watts 3. coulombs": 4exp=1:egc=3:return=432:getans  6"What are the units that charge is measured in ?": Q"1. amps 2. watts 3. coulombs": 4exp=3:egc=3:return=438:getans  "An amp is : 1. 1 coulomb/second 2. 1 coulomb/minute 3. 1 joule/second ?": 4exp=1:egc=3:return=445:getans  scrhdr  497 f"An electric heater runs off 240v and draws ";r(1);" amps. What power does it use ?": Aexp=240*r(1):egc=3:return=455:getans  n"An American electric heater runsoff 110v and draws ";r(1)+10 ;" amps. Whatpower does it use ?": Lexp=110n*r(1)+1100L:egc=3:return=460:getans scrhdr  2n$=c$:start=500:return=498:endsec      current   "Current": "Electric current is the flow of charge from two bodies at different potentials. This can take place through an electric conductor, such as a piece of wire, in which there are free electrons.": scrhdr P"Electrons flowing in a positive direction give rise to a negative current. In a metal, the the velocity at which the electrons drift is quite low - less than one centimeter per second. This is NOT the speed atwhich current flows, as an individual electron does not have to travel the length of a conductor.": scrhdr "When a current flows, the movingcharges are impeded by collisionwith atoms in the conductor. Thecharges give up the energy they have acquired, and electrical power is converted into other forms - for example into heat inthe case of wire.": scrhdr "Current is measured in amps, oneamp representing the flow of onecoulomb of charge in one second.A coulomb is equal to the chargeof six million million million electrons ( 6x10^18 ).":  scrhdr  422  qsthdr "Which is EMF analogous with : 1. rate of flow of electricity 2. quantity of electricity 3. the pressure forcing current to flow ?": 4egc=3:exp=3:return=532:getans  m"An army tank uses a 48v battery,instead of the usual 12v one used in cars. Is this thought of as :": ["1. low 2. high 3. dangerously high ?": 4egc=3:exp=1:return=542:getans  !scrhdr $"Counter EMF is generated by : 1. resistors 2. inductors 3. both resistors and inductors" & (4egc=3:exp=2:return=555+:getans +scrhdr U2n$=c$:start=400:return=598V:endsec V W X Z ]power ` b "Power": dY"Electric power is the product ofelectric current and electromo- tive force, i.e. :": g"power = curent x voltage": hscrhdr j"In a D.C. (direct current) circuit, the current measured inamps multiplied by the voltage measured in volts gives the power in watts.": l"The watt is rather small for most purposes, so the kilowatt (1000 watts) is usual as the unit of electrical power.": mscrhdr n"It is very important to realise that power is measured in watts or kilowatts, NOT watts per houror kilowatts per hour. Power is the rate at which energy is used, one watt being equal to one joule per second.": q?"power = energy / time 1 watt = 1 joule / second": rscrhdr tD"Energy is found by multiplying power by the duration of use :": vA"energy = power x time 1 joule = 1 watt x 1 second": wscrhdr x"The standard unit of electrical energy which appears on electri-city bills is the kilowatt hour.This is the amount of energy used if one kilowatt of power isused for one hour:": {" 1 kilowatt hour =1000 watt hours =1000 x 60 = 60000 watt minutes =60000 x 60 = 3600000 wattsecs =3600000 joules": |scrhdr ~ "So 1 Kwhr = 3600000 Joules": scrhdr qsthdr "Power is measured in ": N"1. Watts/hour 2. watt hours 3. Watts": 4exp=3:egc=3:return=660:getans "Which of these formula is true ? 1. power = current x voltage 2. power = current / voltage 3. power = voltage / current": 4exp=1:egc=3:return=665:getans  450 2n$=c$:start=600X:return=698:endsec     18,0  17,9 ;"Cathode"   " ( z;start=600X:return=898:n$="matrix arithmetic" endsec     electrostatics  "Electrostatics": "So far, current electricity has been described. It involves the flow of current through a circuit. Static electricity is the accumulation of charge on anobject:": scrhdr "Static charges can be built up by friction between insulators. Very high voltages can be produced, but the actual charge is very small.": "Static charges are detected with an electroscope. This is a device which relies on the principle that like charges repel:": scrhdr scrhdr:electroscope:scrhdr M"The greater the angle of deflection, the greater the charge.": scrhdr v"Very high voltages can be produced by a Van der Graaf generator. This consists of a vertical moving insulating belt carrying charge to a large hollow conducting sphere at the top of the generator. Charge is sprayed on at the base of the column, and is picked up by a comb-like electrode in the sphere. Voltages of 1 000 000v can be produced.": scrhdr "Charge is measured in Coulombs, and the ability of a capacitor to store it is measured in Farads. The farad is a very big unit, so the picofarad (10^-12F)is often used instead": ""Charge = capacitance x voltage"   650 qsthdr %"A diode allows current to pass:": ^"1. Both ways 2. one way 3. towards the cathode ?": 4exp=2:egc=3:return=960:getans "A triode :": V"1. amplifies signals 2. is equivalent to a transistor3. both 1. and 2.": 4exp=3:egc=3:return=968:getans "A carrier wave is": ]"1. audio frequency 2. radio frequency 3. carried by the sound": 4exp=2:egc=3:return=978:getans 2n$=c$:start=600X:return=698:endsec      N T    x z     @ B H   scalars and vectors  :"Scalars and vectors": }"Quantities such as mass, volume and length are called SCALAR quantities. Scalar quanties havesize but not direction.": z"Quantities such as velocity and acceleration have both size and direction. Thistype of quantity is called a vector.": D"The general propertyof a vector is that it has two components.": scrhdr qsthdr 1:"Which of these is a vector quantity ? " S:"1. length 2. time 3. velocity": 5exp=3:egc=3:return=1760:getans 3start=1700:return=1798:n$="vectors" endsec      vector arith. & laws  ":"Vector arithmetic and laws": ^"Vector arithmetic is very simpleand follows the laws of conventional arithmetic.": "Addition": <"Two vectors a and b add to make a vector c as follows:": ""a = 2 b = 3":" 1 4" 8i=12 :x=29:y=63?:br:x=93]:br &:"c = 2+3 = 5":" 1+4 = 5" x=101e:y=39':br  x=39':i=24:br !scrhdr $""a = 2 b = 3":" 1 4" &&:"c = 2+3 = 5":" 1+4 = 5" '9i=12 :x=29:y=151:br:x=93]:br (n:"Vector addition is commutative since it makes no difference which way round the vectors are added.": )&x=101e:y=39'+88X:br *x=39':i=24:br +"a + b = b + a = c": ."This is easy to see if you thinkof the vectors as position vectors. It makes no difference which one is taken first - the final position is the same." 0scrhdr 2"vector addition is also associative. Three vectors a, b and c add to make the same result in both of the following ways:": 54" d = a + (b + c) d = (a + b) + c" 8_:"Again, this can be easily understood if the vectors are thought of as positional." :3:"Vector subtraction is also conventional." <scrhdr ?"Vector multiplication": B/"A vector can be multiplied by a scalar:": D1" eg. a = 2 1": F:" eg. 2a = 2 x 2 = 4 2 x 1 = 2" GFi=12 :x=165:y=87W:br:x=77M:y=111o:br H(i=44,:x=85U:y=87W:br Iscrhdr Lqsthdr N/:"Is vector addition commutative ?":a$:a$ P;a$="No"a$="no""Yes it is ! Read the section again." Sa$="yes"a$="Yes"praise V(:"Is vector addition associative ?": X a$:a$ Z;a$="No"a$="no""Yes it is ! Read the section again." ]a$="yes"a$="Yes"praise b=n$="vector arithmetic":start=1800:return=1898j gendsec j k l n qvelocity triangles t v:"Velocity triangles"::"Sometimes it is necessary to know the length of a vector rather than its individual components.": x"Since the two components of a positional vector are at right angles to each other, the lengthof a vector can be calculated using Pythagoras' theorem." yscrhdr {:"For example, the length of a vector:"::" 4":" 3":::::::::"is 5. This can be seen in the triangle above." }1x=14-1:y=119w:i=12 :br ~label=0:triangle O"AB represent a the x component and BC the y component. AC is the length." scrhdr "The length of the vector can represent quantites such as speed. If an aircraft is flying at right angles to the wind its ground speed can be calculated using vectors:":  triangle q"AB represents the aircraft's airspeed, BC represents the wind velocity and AC represents the ground speed." 8,17;"air speed=150":10 ,17;"wind speed=80":12 ,17;"AC=150+80":12 +1,20;"AC=28900":14,21;"AC=170"  :::: scrhdr "Sometimes velocities will not be at right angles. In these cases Puthagorus cannot be used as the resultant triangle is not right angled." d:"The length can be calculated in these cases by drawing the triangle and measuring length." >n$="velocity triangles":start=1900l:return=1998 endsec   x$="": o=1̱x$ n=18 #w(o,n):x$(oo)+n-1,w(o,n) n o  H24,16,16,32 ,16,16,24,0 C24,8,8,4,8,8,24,0 F0,0,62>,64@,64@,64@,62>,0 E0,0,124|,2,2,2,124|,0 G0,66B,66B,66B,66B,66B,44,,0 G0,44,,66B,66B,66B,66B,66B,0  G0,0,60<,64@,124|,64@,60<,0 I240,8,120x,128,248,0,0,0 C0,0,0,4,126~,4,0,0 I248,136,136,136,0,0,0,0 C4,4,228,4,0,0,0,0 G240,8,240,8,240,0,0,0 G28,20,16,16,8,8,40(,568  E4,68D,228,68D,0,0,0,0 "G16,16,16,0,0,480,72H,480 %E12 ,18,18,12 ,0,0,0,0 (E7,4,4,8,8,144,80P,32 *G4,8,16,16,16,32 ,32 ,32 ,G32 ,32 ,32 ,16,16,16,8,4 /C32 ,16,8,8,8,4,4,4 2C4,4,4,8,8,8,16,32 4 )::(40(*3.14159Iρ/180)  z=31000 %v=((z^2-(z-1)^2)) u=v^0.5 C((u)-(u+0.5))<0.01z# =z;":";z-1;":";v^0.5 z  z=07 z:7-z 7x=13:"" c=110 :c x z 0::" G C E TUTORING"::" Orders"  z=025 x=14 code=(c$(xx))+z  code>"z"code=code-26 code; x::z ( X Z ]wiring ` b502,110n:0,40(:40(,0:130,150:40(,0:0,-40(:170,70F:0,-40(:-120x,0:0,40( g   bulb  170+inc,110n z=15 0,-8, z !170+inc,90Z,20     resistor  170,110n z=14 %5,-5:-5,-5 z     meter(type)  110n,150,20 3,14-1;t$ 17,0;" "    " % battery ( *502,110n ,0,-18 /8-10 ,0:20,0:-10 ,0 2502,83S 48-15,0:30,0:-15,0 60,-18 P R T Wlink Z \&90Z,150:40(,0 |   bulbs in series  '170,96`:0,-12 170,103g,7 170,77M,7 170,111o x=14 & 2,-2:-2,-2 x 170,111o-26 x=14 & 2,-2:-2,-2 x     parallel  inc=45-:bulb 9170+inc,70F:0,-40(:-inc,0 9170+inc,110n:0,40(:-inc,0  inc=0    electroscope  502,502 $502,0:0,502 &-502,0:0,-502 75K,115s 0,-45- /75K,115s-37%:4,-7 &60<,115s:30,0  V$7000X:7050:7150 X'170,150:0,40( | ~  triangle VIR  80P,80P <100d,0:-502,86V:-502,-86V 130,80P 70,43+:-25,0:502,0 9 ,12 +1;"I" '9 ,12 +1+5;"R" 4,12 +4;"V" 15,0;" "    diode  502,502 '0,80P:30,0,- 0,-80P -30,0,- 65A,145 %0,-10 :-7,0 14,0 524,43+ x=14 6,0,- x 524,43+ 0,-10 524+24,43+ 0,-10 4,11 ;"Anode" 17,11 ;"Cathode"    triode  "10 ,6;"- - - Grid"  diode D F H Kradio N P502,80P RJ502,0:0,502:-502,0:0,-502 U110n,80P XJ502,0:0,502:-502,0:0,-502 Z170,80P \J502,0:0,502:-502,0:0,-502 v @"A geometric figure can be rotated by multiplying the individual coordinates by one ofthree different transformation matrices, depending on whether rotation through 90,180 or 270 is required.": B&"For a 90 rotation, multiply by:": E" 0 -1":" 1 0": H,"A 90 rotation is shoen in the diagram." I J:"The coordinates of the corners of the triangle are:": L&" 2 2 3":" 2 1 1": MM"which when multiplied by the matrix for a 90 rotation become:": N?" 0 -1 2 0-3 -3 1 0 3 2+0 2": O?" 0 -1 2 0-1 -1 1 0 1 2+0 2": P=" 0 -1 3 0-1 -1 1 0 1 3-0 3" R scrhdr:  Gx,y:0,16,-/3:x+i,y:0,16,/3: "There is a special matrix calledthe UNIT or identity matrix. If another matrix is multiplied by it there is no effect, rather like multiplying a number by 1 in ordinary arithmetic." $:"This is the 2x2 unit matrix:": " 1 0":" 0 1": 'x=8:i=24:y=80P:br scrhdr  " "square + rectangle "]27,568:502,0:0,502:-502,0:0,-502 "_27,568:100d,0:0,502:-100d,0:0,-502 "$7,2;"A D F" "%15,2;"B C E" " " "square + parallelogram "]27,568:75K,0:0,502:-75K,0:0,-502 "`27,568:75K,0:25,502:-75K,0:-25,-502 "#7,3;"A E D F" "!15,3;"B C" " " #K27,568:110n,0:568,41):0,557 #f15,7;"0":15,9 ;"2":15,11 ;"4":15,12 +1;"6" #E14,6;"0":12 ,6;"2":10 ,6;"4" #K27,568:110n,0:568,41):0,557 # [568+16,568+8:0,16:8,-16:-8,0 # ^568+32 ,568+16:0,32 :16,-32 :-16,0 #\568-10 ,568+16:-16,0:16,8:0,-8 #11 ,9 ;"A" #9 ,12 ;"B" #11 ,4;"C" #& #' #( #2K27,41):110n,0:27,41):0,557 #:]17,3;"0":17,6;"2":17,9 ;"4":17,12 ;"6" #<17,15;"8" #>\16,2;"0":14,2;"2":12 ,2;"4":10 ,2;"6" #A #Fi579+x,513+y:20,20:-20,20:-20,-20:20,-20: #Hc72H+x,568+y:0,30:-30,0:0,-30:30,0: #P'"Here is an example of ";n$ #R #Z #\ #_noises #b #d-z=120:0.01z# =,-24:z #f #h #i&z=15:0.3,t(z):z #l #mz=15:t(z):z: #n*7,9 ,5,-7,0 # # # #axes # #_30,90Z:210,0:30,90Z:0,557:0,-110n #10 ,2;"0" #f11 ,9 ;"90":11 ,15;"180":11 ,22;"270":11 ,29;"360" #atype=09124# #atype=19130# #.4,2;"1":16,1;"-1" #07,1;".5":13 ,0;"-.5" # #.7,2;"1":13 ,1;"-1" #.4,2;"2":16,1;"-2" # # # #draw triangle # #N30,60<:100d,0:0,60<:-100d,-60< #label=09175# #15,6;"adjacent" # 8,1;"hypoteneuse" #11 ,18;"opposite" #6123{,60<:0,7:7,0 #H41),60<:0,2:-3,2:-2,0 #14,2;"A" #14,17;"B" #6,17;"C" #::::::::: # # # #"Berk ! What's ";c$;" ?": #'"Wally ! ";c$;" isn't on the tape.": ##"Moron ! Try spelling straight": #"sorry, ";n$;" ? ": #"Are you tired, ";n$;" ?": #"Don't wind me up, ";n$: $T $V scrhdr() $Y $\9900&:: $ $ qsthdr() $ $'9600%:9900&:egc=0: $ $ $endsec(start,n$) $ $7"That finishes: ":n$:"Hit r to repeat this section" $ 9900& $a$="r"start $return $ $ $getans(loop,exp) $ $?dp=0:err=0:u$:u$:(u$)>10 err=1 $(u$)=09460$ $[j=1̱(u$):(u$(jj))<45-ů(u$(jj))>579ů(u$(jj))=47/err=1 $%9480%:j:u$="-."err=1 $Cerr=1dp>1"type the answer as a number":9460$ $=ans=(u$):(exp-ans)>0.005y# ="No, the answer is ";exp $$(ans-exp)0.005y# =9720% $return $ % %$(u$(jj))=46.dp=dp+1 % ,j>1Ư(u$(jj))=45-err=1 %  %k9800H&:d1=r(1)/10 +r(2)/100d+r(3)/1000:dec=d1:int=1000*dec %& %A"See if you understand this by trying the following examples" % 9800H& % %"True or false ?" %a$ %a$ %a$"t"a$"f"9650% % %n:n;"/";:d:d: % 9630% %h"No. Don't add the numbers together. It's just the second number, so the answer is ";r(2) % %K"No, its the second number, not the first, so the answer is ";r(2) % %%9720%+((*9 )+1): % "Good": % "Correct": %"Right again": %"OK": %"That's it": %"Brilliant !": %"Well done": &"Very good": &"Genius !": &HWz=110 :r(z)=(*9 )+1:z:r(1)r(2)9800H&: &R#r(1)r(2)9800H& &\ &z "trap": & &"Hit C to continue" &a$= &a$="c"9950& &a$="r"9950& & 9920& & &z=1502:z & ':"More questions (Y or N)": 't$ ' t$=""9990' ' t$=t$(11) ' t$"y"t$"n"9990' '  32&crhdT$sthd$ndse$etan$ig"iF#xes(#P#xe#riangl#iagrarais%lectroscoparallenriodioderieinRirinXulesistoeteatter qure"qupa"tareturVgxr$n >@@@>||BBBBB,,BBBBB<@|@<x~(8DD0H0  P    X5   TnCseriesSserU1NseriesAceh4  6:6:0: electronics help tape 4  GCE Tutoring !w(25,8):2000 r(10 ) t(5):9069m# Lscrhdr=9300T$:qsthdr=9350$:endsec=9400$:getans=9450$ fig2=8950":fig=9030F#:axes2=9000(#:eg=9040P#:axes=9100#:triangle=9150#:diagram=218:praise=9720% moreq=9980& electroscope=7400:parallel=7350:inc=0:triode=7700:diode=7600:series=7300:link=7250R:wiring=7000X:bulb=7050:resistor=7100:meter=7150:battery=7200  5br=8100:squrec=8850":squpar=8900" )"Electronics help eh4"::"Transducers" :" GCE Tutoring March 1985" 2x:"Hello, what's your name ?":n$:n$:"OK, ";n$;",":"I'll begin by telling you how touse this electronics program." 4W:"This tape covers 5 subjects which all come under the headingof 'Transducers'." :<"Press the key marked C so I can type the next screenful." <a$=:a$="c"62> = 60< >:z=1100d:z AF:"Thanks. From now on when I want you to press the C key, I'll say" D:" Hit C to continue" F4:"Here's the list of subjects on this program": H"introduction microphones loudspeakers heat sensitive devices light sensitive devices" K2:"Which subject do you want to try ?":s$: Lc$=s$ N'(s$)>3s$=s$(13) Os$="int"100d Ps$="mic"200 Qs$="lou" 300, Rs$="hea" 400 Ss$="lig" 500 _ 70F c d f i l n"Transducers": p"A transducer is a device which allows the transmission of energy from one system to another. In electronics this broad definition is more narrow-ly defined by specifying that :": r}"1. either the input or the transducer is electrical 2. the output must be acurately related to its input": tscrhdr vo"Common examples of transducers include microphones, loud- speakers, photocells and thermo-couples.": xM"Transducers are grouped togetherunder a number of different terms :": z_"1. active transducers 2. passive transducers 3. conversion transducers": |#"Let's take these one by one.": }scrhdr ~"Active transducers": "The output of an active trans- ducer, the also needs an external source of power, which is controlled by its input.": scrhdr "Passive transducers": l"The output of a passive trans- ducer is dependant on its input,and needs no external source of power.": scrhdr "Conversion transducers": P"The input and output frequenciesof a conversion transducer are different.": scrhdr qsthdr "A transducer : 1. allows the electrons from one system to flow to another2. allows one system to power another 3. allows the passage of energy from one system to another": 4egc=3:exp=3:return=155:getans  "There are three main types of transducers. Are they : 1. active, passive and capacitive 2. active, potential and control 3. active, passive and conversion ?": 4egc=3:exp=3:return=162:getans "Which type of transducer needs an external power source : 1. active 2. passive 3. conversion ?": 4egc=3:exp=1:return=168:getans scrhdr 2n$=c$:start=100d:return=198:endsec     microphones  "Microphones": u"A microphone is an electro- acoustic transducer. It producesan electrical signal in responseto sound waves.": 3"There are six main types of microphones :": ڶ"1. condenser 2. piezoelectric 3. carbon 4. moving coil 5. ribbon 6. electrostatic": !"Let's take them one by one:": scrhdr "Condenser microphones": "A condenser microphone is a cap-acitor whose capacitance varies with the pressure of the sound waves. This achieved by allowingone of the plates of the capaci-tor to move.": scrhdr 7"The most common way of sensing a capacitance change in a micro-phone of this type is to apply a large DC voltage across the microphone. This should come from a high resistance source, so that the small capacitance ofthe microphone places a signifi-cant load, causing the applied voltage to vary.": scrhdr "Piezoelectric microphones": d"These have the advantage of being passive transducers, and so need no external power source . They consist of a smallpiezoelectric element attached to a thin diaphragm. Pressure changes caused by sound are transmitted by the diaphragm to the piezo crystal, which produces a large electrical signal, but at high impedance.": scrhdr "Piezoelectric microphones are simpler, cheaper and more robustthan condenser types, but are less accurate and have a poorer frequency response.": scrhdr "Carbon microphones": "Carbon microphones consist of a large number of carbon granules whose resistance varies with thepressure of sound waves. An external DC source is needed forthe microphone to produce a varying voltage.": scrhdr "Moving-coil microphones": "This type of microphone consistsof a coil in a strong magnetic field. The coil is attached to adiaphragm, allowing sound waves to move it, thus creating a small voltage at a low impedance.": scrhdr "The response of a moving coil microphone varies with frequency, a higher output beingobtained at high frequencies. External circuitry is used to correct this.": N"Moving coil microphones are widely used in recording studios.": scrhdr "Ribbon microphones": "Also known as pressure gradient microphones, these devices consist of a metal ribbon suspended between the poles of a magnet. The pressure difference induces a voltage in the ribbon proportional to soundpressure.":  scrhdr  "Electrostatic microphones": "This is very similar in prin- ciple to the condenser microphone. It develops a high impedance output, and requires an external high voltage power source.": scrhdr "Which microphones needs external power ? 1. piezoelectric and carbon 2. ribbon and condenser 3. moving coil and electrostatic": 4exp=2:egc=3:return=280:getans  "Which microphone is extensively used in recording studios ? 1. carbon 2. moving coil 3. ribbon": 4egc=3:exp=2:return=286:getans   "Which microphone uses a piece of a ceramic material ? 1. condenser 2. electrostatic 3. piezoelectric": "4egc=3:exp=3:return=292$:getans $scrhdr )2n$=c$:start=200:return=298*:endsec * + . 1loudspeakers 4 6"Loudspeakers": 8"A loudspeaker is a transducer which converts electrical energyinto sound. It consists of a coil of wire in the field of a permanent magnet. The coil is attached to a thin paper or plastic cone, which is flexibly suspended at its outside edge.": :"When an electric current flows through the coil, a force is produced, causing the cone to move. This generates sound waves.": <scrhdr >"Loudspeakers have a low effic- iency, usually around 5%. Efficiencies of between 30% and 50% can be obtained by using a horn of gradually increasing cross-section.": @"Unless extremely large horns areused (3 to 10 metres long), the frequency response is poor, and the horn is only useable for public address systems.": Bscrhdr D"It is difficult to make a loud- speaker of any kind that covers the entire audio spectrum well. To get round this problem, a combination of speakers are used- a 'woofer' for low freque-ncies (30Hz to 4000Hz) and a 'tweeter' for high frequencies (3000Hz to 20000Hz). ": Fscrhdr Hqsthdr J"The efficiency of a typical speaker is approximately : 1. 5% 2. 15% 3. 30% ?": L4egc=3:exp=1:return=335O:getans O R"Another name for a speaker designed for low frequencies is a : 1. horn speaker 2. woofer 3. tweeter ?": T4egc=3:exp=2:return=342V:getans V Y"A loudspeaker converts : 1. sound energy into electrical energy 2. electrical energy into sound energy 3. neither 1. nor 2. ? ": \4egc=3:exp=2:return=350^:getans ^scrhdr 2n$=c$:start=300,:return=398:endsec       #"Temperature sensitive devices": "There are three main types of temperature sensitive transducer 1. thermocouples 2. resistance types 3. thermistors ": "Each of the above devices have different characteristics, and consequently different advantages and disadvantages.": scrhdr "1. thermocouples": "A thermocouple consists of two different metal wires twisted together at one end. It produces a small voltage when heated, which increases with temperature.",: ;"Different combinations of wires produce widely varying voltages.Thermocouples with a comparativ-ely high output (though still measured in millivolts) tend to work over a small temperature range, whereas low output devices, such as a combination of platinum and rhodium, work reliably at over 1600K." scrhdr "2. Resistance types": |"These consist of a conductor wound non-inductively around an insulated former. As temperature increases, the resistance of the device also increases. Highly stable and accurate meas-urements are possible over a large range of tempertures - typically 10 to 1300K." scrhdr "3. Thermistors": "These consist of beads or rods of semi-metal oxides, such as germanium. Unlike the previous type of tra-nsducers, the resistance of a thermistor drops as the tempera-ture increases.": "Thermistors are stable, and have a fast response, but are non- linear (i.e. they do not vary directly with temperature), and consequently require an electronic circuit to converttheir output." scrhdr qsthdr "Which heat sensitive transducer produces a small voltage : 1. thermocouple 2. thermistor 3. resistor ?": 4egc=3:exp=1:return=444:getans  "Which heat sensitive transducer is composed of a semi-metal oxide : 1. thermocouple 2. thermistor 3. resistor ?": 4egc=3:exp=2:return=450:getans "Which of the following has a resistance which decreases rapidly with increasing temper- ature ? 1. thermocouple 2. thermistor 3. resistor": 4egc=3:exp=2:return=455:getans scrhdr 2n$=c$:start=400:return=498:endsec       !"Light sensitive transducers": c"These devices are also known as optical transducers, and can be divided into two main types :": F"1. photosensitive resistors 2. photosensitive semiconductors": n"Each of these types has its own advantages and disadvantages. These are dealt with on the nextfew pages." scrhdr !"1. photosensitive resistors":  V"These devices are also known as light dependent resistors, or LDRs, for short.":  "The commonest material used in LDRs is cadmium sulphide. This compound has a high resistance (>1M) in the dark, and a lower resistance (<100) in bright light.": ?"Another compound that is light sensitive is lead sulphide." scrhdr "Characteristics": "LDRs are sensitive, but respond slowly to changes in light. They are non-linear, which meansthat their conductivity is not directly proportional to the light level." scrhdr "2. photo-semiconductors": "There are two types of photosen-sitive semiconductors a) photodiodes b) phototransistors": t"These devices are both semicond-uctors with the junction exposedto light. This produces extra charge carriers." scrhdr  "a) Photodiodes": ""Current is directly and accurately proportional to the light level. Photodiodes have a very fast response, but give a low output." $scrhdr &"b) Phototransistors": ("These are very similar to photo-diodes, but the current is amplified by the transistor effect. Sensitivity is high, but the response is poorer than that of the photo-diode. Photo-transistors are often combined with a light emiter in the same package. This allows electrical isolation of signals." ) ,scrhdr .qsthdr 0"Cadmium sulphide is used in which of the following optical transducers ? 1. light dependent resistors 2. photodiodes 3. phototransistors": 24exp=1:egc=3:return=5655:getans 5 :"Which of the following optical transducers has the fastest response to a change in light ? 1. light dependent resistors 2. photodiodes 3. phototransistors": <4exp=2:egc=3:return=575?:getans ? D"Which of the following optical transducers has the slowest response to a change in light ? 1. light dependent resistors 2. photodiodes 3. phototransistors": F4exp=1:egc=3:return=585I:getans Iscrhdr U+start=500:return=598V:endsec V W X Z ] ` b"Electronics": d"Electronics differs from what has been covered so far in that it concerns active devices. An active device is one which can in some way control the flow of current, rather than merely passively impede it.": g"The first active device to be invented was the thermionic diode. A diode allows the flow of current in only one directionIt can therefore convert AC to DC.": hscrhdr je"A thermionic diode consists of a filament, a cathode and an anode. The filament is like the filament of a bulb, and heats the the cathode to such a high temperature that some electrons are liberated. These are attracted by the anode, as long as it is positive. If the anode is -ve, the electrons are repelled, and no current flows.": ln"1. The comparator This circuit compares two input signals. If the voltage at the non-inverting input of the op amp is greater than that at the inverting input, then the outputof the op amp rises to the positive supply voltage. If the signals are reversed, the outputfalls to the negative supply voltage.": mscrhdr nscrhdr p"2. Op-amp with feedback": qscrhdr:triode rw"Since A is so large, if Vout is a few volts, then Vin must be very nearly 0 (a virtual earth) since Vout/A 0.": t"The concept of a virtual earth allows the application of Kirchoff's law, which states (more or less) that current can't build up at any point." vscrhdr x"i.e. Iin + If = 0 and Vi/Ri + Vo/Rf = 0 assuming that no current flows into the inverting input": zU"re-arranging the above : Vo = - RfVi/Ri": |scrhdr ~$"3. The non-inverting amplifier": "Unlike the previous circuit, this time the gain is positive. Note that the input to the circuit is connected to the non-inverting input of the op amp.": $"The voltage gain is given by :": "Av = 1 + Rf/Ri": scrhdr &"4. The voltage follower (buffer)": "This circuit is really a specialcase of the previous one where Rf and Ri are both zero. Consequently, it has a gain of one.": D"What is the point of an amplifier with a gain of one ?": &"It's not as silly as it seems...": scrhdr "This circuit has a very high input impedance (much higher than the input impedance of the op amp), but a low output impedance. This makes it useful if a signal mustn't be loaded." 2n$=c$:start=900:return=998:endsec     18,0  17,9 ;"Cathode"   " ( z;start=600X:return=898:n$="matrix arithmetic" endsec     electrostatics  "Electrostatics": "So far, current electricity has been described. It involves the flow of current through a circuit. Static electricity is the accumulation of charge on anobject:": scrhdr "Static charges can be built up by friction between insulators. Very high voltages can be produced, but the actual charge is very small.": "Static charges are detected with an electroscope. This is a device which relies on the principle that like charges repel:": scrhdr scrhdr:electroscope:scrhdr M"The greater the angle of deflection, the greater the charge.": scrhdr v"Very high voltages can be produced by a Van der Graaf generator. This consists of a vertical moving insulating belt carrying charge to a large hollow conducting sphere at the top of the generator. Charge is sprayed on at the base of the column, and is picked up by a comb-like electrode in the sphere. Voltages of 1 000 000v can be produced.": scrhdr "Charge is measured in Coulombs, and the ability of a capacitor to store it is measured in Farads. The farad is a very big unit, so the picofarad (10^-12F)is often used instead": ""Charge = capacitance x voltage"   650 qsthdr %"A diode allows current to pass:": ^"1. Both ways 2. one way 3. towards the cathode ?": 4exp=2:egc=3:return=960:getans "A triode :": V"1. amplifies signals 2. is equivalent to a transistor3. both 1. and 2.": 4exp=3:egc=3:return=968:getans "A carrier wave is": ]"1. audio frequency 2. radio frequency 3. carried by the sound": 4exp=2:egc=3:return=978:getans 2n$=c$:start=600X:return=698:endsec      N T    x z     @ B H   scalars and vectors  :"Scalars and vectors": }"Quantities such as mass, volume and length are called SCALAR quantities. Scalar quanties havesize but not direction.": z"Quantities such as velocity and acceleration have both size and direction. Thistype of quantity is called a vector.": D"The general propertyof a vector is that it has two components.": scrhdr qsthdr 1:"Which of these is a vector quantity ? " S:"1. length 2. time 3. velocity": 5exp=3:egc=3:return=1760:getans 3start=1700:return=1798:n$="vectors" endsec      vector arith. & laws  ":"Vector arithmetic and laws": ^"Vector arithmetic is very simpleand follows the laws of conventional arithmetic.": "Addition": <"Two vectors a and b add to make a vector c as follows:": ""a = 2 b = 3":" 1 4" 8i=12 :x=29:y=63?:br:x=93]:br &:"c = 2+3 = 5":" 1+4 = 5" x=101e:y=39':br  x=39':i=24:br !scrhdr $""a = 2 b = 3":" 1 4" &&:"c = 2+3 = 5":" 1+4 = 5" '9i=12 :x=29:y=151:br:x=93]:br (n:"Vector addition is commutative since it makes no difference which way round the vectors are added.": )&x=101e:y=39'+88X:br *x=39':i=24:br +"a + b = b + a = c": ."This is easy to see if you thinkof the vectors as position vectors. It makes no difference which one is taken first - the final position is the same." 0scrhdr 2"vector addition is also associative. Three vectors a, b and c add to make the same result in both of the following ways:": 54" d = a + (b + c) d = (a + b) + c" 8_:"Again, this can be easily understood if the vectors are thought of as positional." :3:"Vector subtraction is also conventional." <scrhdr ?"Vector multiplication": B/"A vector can be multiplied by a scalar:": D1" eg. a = 2 1": F:" eg. 2a = 2 x 2 = 4 2 x 1 = 2" GFi=12 :x=165:y=87W:br:x=77M:y=111o:br H(i=44,:x=85U:y=87W:br Iscrhdr Lqsthdr N/:"Is vector addition commutative ?":a$:a$ P;a$="No"a$="no""Yes it is ! Read the section again." Sa$="yes"a$="Yes"praise V(:"Is vector addition associative ?": X a$:a$ Z;a$="No"a$="no""Yes it is ! Read the section again." ]a$="yes"a$="Yes"praise b=n$="vector arithmetic":start=1800:return=1898j gendsec j k l n qvelocity triangles t v:"Velocity triangles"::"Sometimes it is necessary to know the length of a vector rather than its individual components.": x"Since the two components of a positional vector are at right angles to each other, the lengthof a vector can be calculated using Pythagoras' theorem." yscrhdr {:"For example, the length of a vector:"::" 4":" 3":::::::::"is 5. This can be seen in the triangle above." }1x=14-1:y=119w:i=12 :br ~label=0:triangle O"AB represent a the x component and BC the y component. AC is the length." scrhdr "The length of the vector can represent quantites such as speed. If an aircraft is flying at right angles to the wind its ground speed can be calculated using vectors:":  triangle q"AB represents the aircraft's airspeed, BC represents the wind velocity and AC represents the ground speed." 8,17;"air speed=150":10 ,17;"wind speed=80":12 ,17;"AC=150+80":12 +1,20;"AC=28900":14,21;"AC=170"  :::: scrhdr "Sometimes velocities will not be at right angles. In these cases Puthagorus cannot be used as the resultant triangle is not right angled." d:"The length can be calculated in these cases by drawing the triangle and measuring length." >n$="velocity triangles":start=1900l:return=1998 endsec   x$="": o=1̱x$ n=18 #w(o,n):x$(oo)+n-1,w(o,n) n o  H24,16,16,32 ,16,16,24,0 C24,8,8,4,8,8,24,0 F0,0,62>,64@,64@,64@,62>,0 E0,0,124|,2,2,2,124|,0 G0,66B,66B,66B,66B,66B,44,,0 G0,44,,66B,66B,66B,66B,66B,0  G0,0,60<,64@,124|,64@,60<,0 I240,8,120x,128,248,0,0,0 C0,0,0,4,126~,4,0,0 I248,136,136,136,0,0,0,0 H0,24,36$,66B,36$,36$,102f,0 G240,8,240,8,240,0,0,0 G28,20,16,16,8,8,40(,568  E4,68D,228,68D,0,0,0,0 "G16,16,16,0,0,480,72H,480 %E12 ,18,18,12 ,0,0,0,0 (E7,4,4,8,8,144,80P,32 *H0,0,16,40(,68D,130,254,0 ,G32 ,32 ,32 ,16,16,16,8,4 /C32 ,16,8,8,8,4,4,4 2C4,4,4,8,8,8,16,32 4 )::(40(*3.14159Iρ/180)  z=31000 %v=((z^2-(z-1)^2)) u=v^0.5 C((u)-(u+0.5))<0.01z# =z;":";z-1;":";v^0.5 z  z=07 z:7-z 7x=13:"" c=110 :c x z 0::" G C E TUTORING"::" Orders"  z=025 x=14 code=(c$(xx))+z  code>"z"code=code-26 code; x::z ( X Z ]wiring ` b502,110n:0,40(:40(,0:130,150:40(,0:0,-40(:170,70F:0,-40(:-120x,0:0,40( g   bulb  170+inc,110n z=15 0,-8, z !170+inc,90Z,20     resistor  170,110n z=14 %5,-5:-5,-5 z     meter(type)  110n,150,20 3,14-1;t$ 17,0;" "    " % battery ( *502,110n ,0,-18 /8-10 ,0:20,0:-10 ,0 2502,83S 48-15,0:30,0:-15,0 60,-18 P R T Wlink Z \&90Z,150:40(,0 |   bulbs in series  '170,96`:0,-12 170,103g,7 170,77M,7 170,111o x=14 & 2,-2:-2,-2 x 170,111o-26 x=14 & 2,-2:-2,-2 x     parallel  inc=45-:bulb 9170+inc,70F:0,-40(:-inc,0 9170+inc,110n:0,40(:-inc,0  inc=0    electroscope  502,502 $502,0:0,502 &-502,0:0,-502 75K,115s 0,-45- /75K,115s-37%:4,-7 &60<,115s:30,0  V$7000X:7050:7150 X'170,150:0,40( | ~  triangle VIR  80P,80P <100d,0:-502,86V:-502,-86V 130,80P 70,43+:-25,0:502,0 9 ,12 +1;"I" '9 ,12 +1+5;"R" 4,12 +4;"V" 15,0;" "    diode  502,502 '0,80P:30,0,- 0,-80P -30,0,- 65A,145 %0,-10 :-7,0 14,0 524,43+ x=14 6,0,- x 524,43+ 0,-10 524+24,43+ 0,-10 4,11 ;"Anode" 17,11 ;"Cathode"    triode  "10 ,6;"- - - Grid"  diode D F H Kradio N P502,80P RJ502,0:0,502:-502,0:0,-502 U110n,80P XJ502,0:0,502:-502,0:0,-502 Z170,80P \J502,0:0,502:-502,0:0,-502 v @"A geometric figure can be rotated by multiplying the individual coordinates by one ofthree different transformation matrices, depending on whether rotation through 90,180 or 270 is required.": B&"For a 90 rotation, multiply by:": E" 0 -1":" 1 0": H,"A 90 rotation is shoen in the diagram." I J:"The coordinates of the corners of the triangle are:": L&" 2 2 3":" 2 1 1": MM"which when multiplied by the matrix for a 90 rotation become:": N?" 0 -1 2 0-3 -3 1 0 3 2+0 2": O?" 0 -1 2 0-1 -1 1 0 1 2+0 2": P=" 0 -1 3 0-1 -1 1 0 1 3-0 3" R scrhdr:  Gx,y:0,16,-/3:x+i,y:0,16,/3: "There is a special matrix calledthe UNIT or identity matrix. If another matrix is multiplied by it there is no effect, rather like multiplying a number by 1 in ordinary arithmetic." $:"This is the 2x2 unit matrix:": " 1 0":" 0 1": 'x=8:i=24:y=80P:br scrhdr  " "square + rectangle "]27,568:502,0:0,502:-502,0:0,-502 "_27,568:100d,0:0,502:-100d,0:0,-502 "$7,2;"A D F" "%15,2;"B C E" " " "square + parallelogram "]27,568:75K,0:0,502:-75K,0:0,-502 "`27,568:75K,0:25,502:-75K,0:-25,-502 "#7,3;"A E D F" "!15,3;"B C" " " #K27,568:110n,0:568,41):0,557 #f15,7;"0":15,9 ;"2":15,11 ;"4":15,12 +1;"6" #E14,6;"0":12 ,6;"2":10 ,6;"4" #K27,568:110n,0:568,41):0,557 # [568+16,568+8:0,16:8,-16:-8,0 # ^568+32 ,568+16:0,32 :16,-32 :-16,0 #\568-10 ,568+16:-16,0:16,8:0,-8 #11 ,9 ;"A" #9 ,12 ;"B" #11 ,4;"C" #& #' #( #2K27,41):110n,0:27,41):0,557 #:]17,3;"0":17,6;"2":17,9 ;"4":17,12 ;"6" #<17,15;"8" #>\16,2;"0":14,2;"2":12 ,2;"4":10 ,2;"6" #A #Fi579+x,513+y:20,20:-20,20:-20,-20:20,-20: #Hc72H+x,568+y:0,30:-30,0:0,-30:30,0: #P'"Here is an example of ";n$ #R #Z #\ #_noises #b #d-z=120:0.01z# =,-24:z #f #h #i&z=15:0.3,t(z):z #l #mz=15:t(z):z: #n*7,9 ,5,-7,0 # # # #axes # #_30,90Z:210,0:30,90Z:0,557:0,-110n #10 ,2;"0" #f11 ,9 ;"90":11 ,15;"180":11 ,22;"270":11 ,29;"360" #atype=09124# #atype=19130# #.4,2;"1":16,1;"-1" #07,1;".5":13 ,0;"-.5" # #.7,2;"1":13 ,1;"-1" #.4,2;"2":16,1;"-2" # # # #draw triangle # #N30,60<:100d,0:0,60<:-100d,-60< #label=09175# #15,6;"adjacent" # 8,1;"hypoteneuse" #11 ,18;"opposite" #6123{,60<:0,7:7,0 #H41),60<:0,2:-3,2:-2,0 #14,2;"A" #14,17;"B" #6,17;"C" #::::::::: # # # #"Berk ! What's ";c$;" ?": #'"Wally ! ";c$;" isn't on the tape.": ##"Moron ! Try spelling straight": #"sorry, ";n$;" ? ": #"Are you tired, ";n$;" ?": #"Don't wind me up, ";n$: $T $V scrhdr() $Y $\9900&:: $ $ qsthdr() $ $'9600%:9900&:egc=0: $ $ $endsec(start,n$) $ $7"That finishes: ":n$:"Hit r to repeat this section" $ 9900& $a$="r"start $return $ $ $getans(loop,exp) $ $?dp=0:err=0:u$:u$:(u$)>10 err=1 $(u$)=09460$ $[j=1̱(u$):(u$(jj))<45-ů(u$(jj))>579ů(u$(jj))=47/err=1 $%9480%:j:u$="-."err=1 $Cerr=1dp>1"type the answer as a number":9460$ $=ans=(u$):(exp-ans)>0.005y# ="No, the answer is ";exp $$(ans-exp)0.005y# =9720% $return $ % %$(u$(jj))=46.dp=dp+1 % ,j>1Ư(u$(jj))=45-err=1 %  %k9800H&:d1=r(1)/10 +r(2)/100d+r(3)/1000:dec=d1:int=1000*dec %& %A"See if you understand this by trying the following examples" % 9800H& % %"True or false ?" %a$ %a$ %a$"t"a$"f"9650% % %n:n;"/";:d:d: % 9630% %h"No. Don't add the numbers together. It's just the second number, so the answer is ";r(2) % %K"No, its the second number, not the first, so the answer is ";r(2) % %%9720%+((*9 )+1): % "Good": % "Correct": %"Right again": %"OK": %"That's it": %"Brilliant !": %"Well done": &"Very good": &"Genius !": &HWz=110 :r(z)=(*9 )+1:z:r(1)r(2)9800H&: &R#r(1)r(2)9800H& &\ &z "trap": & &"Hit C to continue" &a$= &a$="c"9950& &a$="r"9950& & 9920& & &z=1502:z & &Cmore=0:"More questions ? (y or n)":e$:e$=""9980& &?e$(11)="y"e$(11)="Y"more=1 & '  m#crhdT$sthd$ndse$etan$ig"iF#xes(#P#xe#riangl#iagrarais%ore&lectroscoparallenriodioderieinRirinXulesistoeteatter qure"qupa"tareturVgxr$nU3NnickAcClllllllllllllllSlll >@@@>||BBBBB,,BBBBB<@|@<x~$B$$f(8DD0H0  P (D   X5