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higher education & training Department: _ Higher Education and Training REPUBLIC OF SOUTH AFRICA QUESTION & SOLOTION INDUSTRIAL ELECTRONICS N3 MR GUIDEMAN | 072 1850 565 Please turn over Copyright reserved Downloaded from hlayiso.com

(8080613) -3- T640(E)(J29)T QUESTION 1: DIRECT-CURRENT THEORY 1.1 Indicate whether the following statement is TRUE or FALSE. Choose the answer and write only ‘true’ or ‘false' next to the question number (1.1) in the ANSWER BOOK. Kirchhoff's first law is applicable to series circuits. (1) 1.2 Define Kirchhoff's second law. (2) 1.3 aed FIGURE 1 below and determine the following with the aid of Kirchhoff's jaws: : 1,-0,012A rr 50 V FIGURE 1 1.3.1 The equation for loop 1 (ABDA) (2) 1.3.2 The equation for loop 2 (BCDB) (2) 1.3.3 The magnitude of the currents 7, and J, by making use of the equations in QUESTION 1.3.1 and QUESTION 4.3.2. a Copyright reserved Please turn over Downloaded from hlayiso.com

4. T640(E)(J29)T 4 (8080613) ( QUESTION 2; ALTERNATING-CURRENT THEORY | or FALSE. Choose the icate whether the following statement is TRUE : lenis a tion number (2.1) in the answer and write only ‘true’ or ‘false’ next to the ques ANSWER BOOK. 2.1 opi oee The inductive reactance of an inductor is directly proportional to the at frequency. ) 22 An RLC series circuit with values R = 150 , L = 23 mH and with a capacitor of 52 uF respectively is connected to a supply voltage of 220 V and a frequency of 50 Hz. Determine the following: ; 2.2.1 Inductive reactance (1) 2.2.2 Capacitive reactance a) 5 2.2.3 Total current ) 3 2.2.4 Phase angle Hl ; ; : i 4 i ? Downloaded from hlayiso.com ; ‘cop Copyright reserved Please turn over 2 nil ia

(8080613) QUESTION 3: SEMICONDUCTOR PHYSICS AND SILICON-CONTROLLED RECTIFIERS 3.1 Indicate whether the following statements are TRUE or FALSE. Choose the answer and write only ‘true’ or ‘false’ next to the question number (3.1.1-3.1.2) in the ANSWER BOOK. 3.1.1 Should an atom lose an electron, it becomes a negative ion because it now possesses more protons than electrons. 3.1.2 An SCR has three junctions. (2 * 1) 3.2 Various options are given as possible answers to the following questions. Choose the answer and write only the letter (A-D) next to the question number (3.2.1—3.2.2) in the ANSWER BOOK. 3.2.1 The movement of charges of the same type from a high concentration of free-charge carriers to a low concentration of free- charge carriers is called ... A drift current. B_ diffusion current. C acceptor doping. D_ donor doping. 3.2.2 Transients are at their worst when an SCR is switched on at ... A 30°. B 45°. Cc 90°. D 18°. Bud valence elect an atom. Describe the valence bands of the following materials: 33.1 conductor 3.3.2 insulator 3.3.3 resistor 3.3.4 semi-conductor = T640(E)(J29)T (2 * 1) An atom loses, gains or shares valence electrons with others. It is these rons that determine the electrical or the chemical properties of (2) (2) Please turn over Bepynght uaa Downloaded from hlayiso.com

T640(E)(J29)T -~6- (8080613) TWO transistors. 3.4 Draw a transistor-equivalent circuit of an SCR by means of (5) Q Also show the anode, the cathode and the gate. = : i ntered. . 3.5 When an SCR is switched on, the problem of transients is encou . ; (3) Name THREE methods of eliminating these transients. [16] 5. QUESTION 4: DIODES AND THEIR APPLICATIONS i stion. 41 Various options are given as possible answers to the ied ‘uestion Choose the answer and write only the letter (A-C) next to number (4.1) in the ANSWER BOOK. Since diodes are destroyed by excessive current, circuits must have a ... 5 5 A high-voltage source. B high-current source, 1 Cc Ccurrent-limiting resistor. (1) 4.2 Draw a neat, labelled circuit diagram of a positive series clipper. Show the 15 input and output waveforms. 5 4.3 Give ONE word/term for each of the following descriptions by choosing a word/term from the list below. Write only the word/term next to the question number (4.3.1-4.3.5) in the ANSWER BOOK. Q ; photodiode; varactor diode: Zener diode; ~PNjunction diode light-emitting diode 4.3.1 Under forward-bias Conditions this diode acts as a Conductor and it is used as a rectifier. 4.3.2 This diode operates under reverse-bias conditions and is used as a detector. 4.3.3 This diode radiates light and is used in read-out devices. 6 4.3.4 This diode operates under reverse-bias conditions and is also known as voltage-variable Capacitance diodes. 4.3.5 This diode operates under reverse-bias conditions as a voltage reference source. ° (5x1) (5) | (11) | Downloaded from hlayiso.com 6.

(8080613) -7- T640(E)(J29)T QUESTION 5: TRANSISTORS 5.1 Indicate whether the following statement is TRUE or FALSE. Choose the answer and write only 'true' or 'false' next to the question number (5.1) in the ANSWER BOOK. Bipolar transistors are current-operated devices. (1) 5.2 Briefly describe the operation of each of the following amplifiers and give a use of each: 5.2.1 Class A S22 Class B (2 x 3) (6) 5.3 Name THREE regions under which a transistor can operate. (3) 5.4 Draw and label the following IEC symbols: 5.4.1 Phototransistor 5.4.2 P-channel enhancement MOSFET (2 x 2) (4) 6.5 Draw the characteristic curve of an N-channel JFET transistor. (3) (17) QUESTION 6: OPERATIONAL AMPLIFIERS 6.1 Various options are given as possible answers to the following question. Choose the answer and write only the letter (A-C) next to the question number (6.1) in the ANSWER BOOK. The operational amplifier of which gain is always more than one is the ... A _ inverting amplifier. B non-inverting amplifier. C voltage follower. (1) 3.2 Draw the output waveforms for each of the following operational amplifiers if the input waveform for each operational amplifier is a sine wave of 720°. 6.2.1 Integrator 6.2.2 Differentiator 6.2.3 Summing amplifier (3 * 2) (6) 3 Name FOUR advantages of operational amplifiers. (4) [11] Downloaded from hlayiso.com -Opyright reserved Please turn over

ee QUESTION 7: TRANSDUCERS ers to the following question, 5 possible oer (A-C) next to the question e lel . ; a 7.4 Various options are given © ny th Choose the answer ann ER BOOK. number (7.1) in the A An LVDT can be used to measure ..- A distance, force and direction. B distance, speed and dredion (1 H nd speed. ; C distance, force and sp considered when selecting the 7.2 Name THREE points that need to be (3) transducer. . ; cer. 7.3 Name THREE applications of a piezo-electric transd (3) F e bridge. 74 FIGURE 2ebelow is a strain gauge used inva Wheatstone bncg Active Ri eran SS 8 Or i compensation strain gauge Source —— voltage FIGURE 2 7.4.1 Briefly explain the operating principle of the transducer in FIGURE 2. 7.4.2 Name TWO areas of its application. (2*2) (4) [11] QUESTION 8: MEASURING INSTRUMENTS 8.1 Draw a neat, labelled block di ; or - voltmeter lagram of a Successive-approximation digital , (7) 8.2 Explain the purpose of a cathode- . p purp ode-ray tube as used in an oscilloscope. (2) 8.3 Name THREE broad categories in whj ini classified. hich a digital voltmeter (DVM) can be , ( (12) Downloaded from hlayiso.com Tora: 100 d

NN ON INDUSTRIAL ELECTRONICS N3 QUESTION 1 | 141 False (1) 1.2 In a closed loop, the algebraic sum of the EMF acting around the loop is equal a to the algebraic sum of the potential differences around that loop. 43 131 Ril +Rs(0,012) — Rabe = 0 10h; + 0,06 — 251, = OV 101, — 251g = -0,06 ---—-—-—-(1) (2) 1.3.2 Ro(ly — 0,012) — Ra(l2 + 0,012) — Rs(0,012) = 0 151; — 0,18 — 20lz — 0,24 — 0,06 = Ov 15h, — 20l2 = 0,48 -------—---- (2)¥ (2) 1.3.3 (1)x3 : 30h —75l2= -0,18 (2)x-2 : -30l, + 40l2 = -0.96 -35l2 = -1,14” lo = 1,14/35 lk = 0,033 AY or 32,571mMA Substitute lp in equation 1 401, — 25(0,033) = -0,06 |, = -0,06 + 0,825” 10 = 0,077 AY or 75,429mA (4) {11} QUESTION 2 2.4 True (1) 2.2 2.2.4 X. = 2nfL me =2x1x 50x 23x10" ‘ = 7,226 OY , (1) 2.2.2 Xe = 1/2mfC = 1/2m x 50 x 52 x 10° (1) = 61,2130" where Zr = NPR? + (Xe— X1)* = 220/159,419 Vv > = 1,38 AY = \[ 4502 + (61,213 — 7,226)?” _—_—_—_—_»> _ = 159,419 OV Downloaded from hlayiso.com 2.2.3 Ty = WZr Please turn over

| TE40(E\27 | -12- MARKING GUIDELINE INDUSTRIAL ELECTRONICS N3 Cos @, = R/Z 2.2.4 Q.= Cos 1(150/159,419)¥ “ QUESTION 3 3.1 3.1.1 False 3.1.2 False (2 « 1) 3.2 3.2.1 B 2.2 Cc ° (2 * 1) 3.3 e Aconductor is an atom with less than FOUR valence electrons. ¢ An insulator is an atom with exactly EIGHT valence electrons. ¢ Aresistor is an atom with more than FOUR valence electrons. ¢ Asemiconductor is an atom with exactly FOUR valence electrons. 3.4 A py. Ine! / \a B1 ‘c2 —> i c2 G ea my, ee yT2 igo “IA H Kov¥YYv Atmark at A, G, K, as well as each correctly configured transistor 3.5 eLC filters Zener diodes eTrans-zorps Varistors (Any 3 x 1) Downloaded from hlayiso.com Copyright reserved : ppp (3) [11] (2) (2) (3) [16] Please turn over ce 4 y. ce

T640(E)(U29)T | MARKING GUIDELINE -13- i INDUSTRIAL ELECTRONICS N3 3) QUESTION 4 } (1) 41 Cc 4.2 v Vin D, v ' Ry | |“ Vout v (5) 4.3 4.3.1 PNijunction diode 4.3.2 Photodiode i 4.3.3 Light-emitting diode 4.3.4 Varactor diode } 4.3.5 Zener diode (5 * 1) (5) | [11] QUESTION 5 51 True (1) In class A amplifiers the bias point corresponds to the mid-point of 5.2 5.2.1 the active region of the characteristic curveY and is selected so that the current flows during the whole of the input cycle. v It is used in audio amplifiers.“ | 5.2.2 In class B amplifiers the bias point corresponds to the cut-off region of the characteristic curvew and the current flows only during the positive half cycles of the signal voltage.” It is used in audio amplifiers. ” (2x3) (6) 3 ¢ Cut-off region e Active or linear region (3 x 1) (3) e Saturation region 4 5.4.4 ¢ \. vv Downloaded from hlayiso.com Please turn over pyright reserved

T640(E)(J29)T -14- INDUSTRIAL ELECTRONICS N3 MARKING GUIDELINE i Drain 5.4.2 Substrate Gate v (4) (2x 2) Ves=OV v 15 Vos(v)Y 10 v Source To j (mA) v 5.5 QUESTION 6 (1) 7.4 6.2.3 Vin Vin Downloaded from hlayiso.com Copyright reserved Opyrig a Please turn over

| MARKING GUIDELINE -15- T640(E)(J29)T INDUSTRIAL ELECTRONICS N3 6.3 eThey are small in size. They have low power consumption. They are highly stable. eThey are cheap. They are highly reliable. Characteristics may be considered as advantages as well, eg. high gain, low output impedance (Any 4 * 1) (4) [11] QUESTION 7 7.1 A (1) 7.2 ¢ The physical quantity that needs to be measured * The converting principle which is most suitable ¢ The accuracy that is required (3 « 1) (3) 1.3 e Sound « Acceleration e Vibration ¢ Pressure changes (Any 3 x 1) (3) 7.4 7.4.1 The resistance of a wire is changed by expansion and contraction due to externally applied stress. (2) 7.4.2 To Measure/ determine ¢ Displacement e Pressure/Force « Torque (Any 2 x 1) (2) [11] Downloaded from hlayiso.com Please turn over pyright reserved

T (8080613) S40(E\J29)7 QUESTION 8 841 “% ox comparator analogue \, vy a on [x unknown = % oa voltage > a ty" momo L nasil | 82 The cathode-ray tube ( RT) produces a sharply focused beam of electrons and accelerates it to @ very high velocity to strike the fluorescent screen with enough energy to light up in a small spate" nm 83 ° Ramp type er * Continuous balance H } * Successive approximation ff & Integrating A J ff (Any 3 « 1) a) , . 4 ‘ é , ey rd b t, i , TOTAL tog Neh, > ™merved Downloaded from hlayiso.com Re nent

eo QUESTION 1: DIRECT-CURRENT THEORY 1.1 1.2 . Define the first law of Kirchoff as applicable to parallel circuits. Determine the currents |), lz, Is and [4 in the network in FIGURE 1 on the DIAGRAM SHEET (attached) by making use of Kirchhoff's laws. QUESTION 2: ALTERNATING-CURRENT THEORY 2.1 Indicate whether the following statements are TRUE or FALSE. Choose the answer and write only ‘true’ or ‘false’ next to the question number (2.1.1-2.1.5) in the ANSWER BOOK. 2.1.1 2.1.2 Resonance takes place in a series RL circuit. A series RLC circuit reacts inductively below resonance. A series-resonant circuit will always amplify the current in the circuit. The inductive reactance of an inductor is inversely proportional to the frequency of the circuit. Resistance in an RLC circuit is not affected by the change in frequency. (5 x 1) 2 A coil of 0,19 H with a resistance of 25 Q is connected in series with a capacitor of 125 wF across a 200 V/50 Hz alternating supply. Calculate the following: 2.2.1 2.2.2 2.2.3 2.2.4 2.2.5 yright reserved The inductive reactance of the inductor The capacitive reactance of the capacitor The total impedance of the circuit The phase angle between the current and the voltage. The voltage drop across the coil \ a ; [ Please turn over (3) (8) [11] (5)

HyYSICS plicable to sem'< diode as applicable to Semicondueto, a P QUESTION 3: SEMICONDUCTOR onductors. , as ap. 3.1 Define the term drift current Ic) of 3.2 Define the term forward current (Ir) diodes. g of the Fermi-level in the — e positionin 3.3 Make labelled sketches to indicate the P following materials: 3.3.1 P-type material 3.3.2 N-type material 3.3.3 Intrinsic material (3x 3) ive ion with regard to atoms. 3.4 Differentiate between a positive ion and a negative ion QUESTION 4: DIODES AND THEIR APPLICATIONS 41 Draw a circuit diagram of a negative series clipper as well as of its input ang output waveforms. 4.2 Give THREE uses of a light-emitting diode in diode applications. 4.3 Draw the characteristic curve of a photodiode as applied in semiconductor diodes. QUESTION 5: TRANSISTORS Refer to FIGURE 2 on the DIAGRAM SHEET (attached) and make use of the values to calculate the following: 5.1 The maximum value of Ic to enable you to plot the DC load line 5.2 The maximum value of Vcr to enable you to plot the DC load line 5.3 The value of leq) if the Q-point is selected in the active region 5.4 The maximum value of le when Re is now changed to 4 kQ Downloaded from hlayiso.com Copyright reserved 108¢ ‘UE Q r Q2 (9 {tt ef Please tum ™

(8080613) -5- QUESTION 6: SILICON-CONTROLLED RECTIFIERS (SCR) 3 4 Name THREE applications of an SCR. $2 Briefly explain the term forced commutation as applicable to an SCR. 3 Name FOUR methods used to Suppress transients in an SCR. 4 Draw a neat, labelled characteristic curve of an SCR. UESTION 7: OPERATIONAL AMPLIFIERS 4 Give FOUR main advantages of an operational amplifier. 2 Draw a neat circuit of the volta ge follower as applicable to operational amplifiers. UESTION 8: TRANSDUCERS 1 Briefly describe the operating principle of a Wheatstone bridge as applied with transducers. ) Explain the difference between PTC and NTC thermistors with respect to temperature and resistance. JESTION 9: MEASURING INSTRUMENTS Draw the block diagram of a frequency counter as applicable to measuring instruments. Describe the operation of the frequency counter in QUESTION 9.1 above as applicable to measuring instruments. TOTAL: Downloaded from hlayiso.com T720(E)(A11)T [14] (4) (4) 3] (5) (5) [10] 100

ee BE IEERIENSEANTT DIAGRAM SHEET NDL OR L 0,34 lirec 2,5A |_ _____»>— p= Jter 03A a FIGURE 1 T= Vec=12V =] | “ Io r= Ip -—— { | > _ =t FIGURE 2 pS rans rans is ; . Opyri Copyright reserved Downloaded from hlayiso.com

T720(E)(A4)> MARKIN IG GUIDELINE 2. INDUSTRIAL ELECTRONICS N3 - QUESTION 1 ards a junction’ is equal to 1.4 Kirchhoff's fi : ing tow: 's first law: The total current flowing 3 a, the total sum” of the currents flowing away from that junction. (8 1.2 =(0,6+0,9)=1,5A lb =(2,5-1,5)=1A ls = (1,6 +0,3)=1,9A (8 I, = (0,9-0,3)=0,6A tt QUESTION 2 False False False UE False True 4 (5x1) 2.1 NNNNN uneted a AhwWhy a 2.2 2.2.1 X= 27 =2 x 3,142 x 50 x 0,19 (l X_= 59,6980 v 3 _ 1 Soi X= 2€3,142x50% 125x108 | Xc = 25,461 Q v 2.23 Zr= R2+(XL-Xc)? Zr= /(25)* + (34,237)? v : Zr = 42,393 0 v 2.2.4 Cos 9 = = - 12s 8 = Cos 42,393 v (2 @ = 53,863 °v Downloaded from hlayiso.com eet me

MARKING GUIDELINE ie T720(E)(A4)T INDUSTRIAL ELECTRONICS N3 2.2.5 Zeai =f R2 + X2 = (25)? +(59,698)2v 3 ) Zool = 64,7210 v eS AND 200 42,393 Ir=4718A v Therefore: Veoit = It x Zeoil = 4,718 x 64,721 v Veoi = 305,353 Vv (5) [16] QUESTION 3 . 3.1 It is the type of current which flows across a semiconductor material when it is 7) connected to a voltage source. (2) 8.2 It is the maximum amount of current the diode can handle when forward 1 biased. (2) 3.3 3.3.1 P-type material: ) Conduction band v Fermi-level closer to valence band ) Fermi-level Vv v Valence band f 4 Downloaded from hlayiso.com Please turn over ee Opyright reserved RE est

4. T720(E)(A4yy MARKING GUIDELINE INDUSTRIAL ELECTRONICS N3 a 3.3.2 N-type material: 3 Conduction band v Fermi-level closer to conduction band Fermi-level v Valence band e 3.3.3 Intrinsic material: Conduction band a Fermi-level in the middle Fermi-level v Valence band v (3x3) 3.4 A positive ion is an atom which has lost an electron whereas a negative ion is ' an atom which has gained an extra electron. ( (1 QUESTION 4 v 41 PNY v | v v ( 4.2 LEDs can be used in alphanumeric displays, remote controls, 7-segment displays, security systems, and any other practical application. (Any3x1) | Downloaded from hlayiso.com Copyright reserved Please turn ove!

t T720(E)(A4)T -5- (ARKING GUIDELINE } INDUSTRIAL ELECTRONICS N3 4.3 vy -20 800 lux 45 600 lux ~ 10 400 lux 5 200 |ux 0 T T T Ls v 2 4 6 8 a (3) [10] QUESTION 5 5 _ vec ‘4 loqmax) = > =v 2105 Iowan =6 MA v (2) 2 Vee = Vee = 12 V (Assumption) (1) 3 loa) = — v loray =3 mAY (2) 4 lommaxy = ae = 82 $x10° (2) lemax)= 3 MAY [7] Downloaded from hlayiso.com yright reserved Please turn over

EE ————— a i T720(E)(A4)y Be ics N3 MA RKING GUIDELINE STRIAL ELECTRON INDU: QUESTION 6 6.1 Car ignitions Regulated power supplies Inverters Choppers Lamp dimmer relay controls Speed control of small motors (Any 3 * 1) n SCR off ina DC circuit. to switch a rection opposite to the sed : method u to flow in the di 6.2 Forced commutation is a rced The current through the SCR is fol forward conducting current. 6.3 e Zener diodes e Varistors e LC filters e Tranzorps 6.4 Forward Conducting v Region Reverse Breakdown Voltage yo Von Veo v -A 1 mark x 2 for correct drawing in left and right quadrants, including drawing axis 4 mark x 2 for correct labelling of left and right quadrants, including labelling the axis Downloaded from hlayiso.com ) Please tum ovél Copyright reserved KRY (: t

MARKING GUIDELINE -7- TT20(E)(A4)T INDUSTRIAL ELECTRONICS N3 QUESTION 7 71 e Small size e Low power consumption e Highly stable e Cheap (4) (f2 v 4 mark for each terminal and 1 mark for the feedback line (4 QUESTION 8 3.1 The current flow through the galvanometer depends on the potential difference across the galvanometer. If the bridge is balanced then the potential difference across the meter will be zero as there is no current flow through the meter. This balanced condition allows us to determine the value of the unknown resistor if the other three resistors are known. (Any other logical description is acceptable.) (4) 3.2 PTC thermistor ~ Resistance is directly proportional to temperature; when temperature increases or decreases resistance will also change in the same direction. NTC thermistor — Resistance is inversely proportional to temperature; when temperature increases or decreases resistance will change in the opposite direction. (4) [8] 14 Downloaded from hlayiso.com piease tum over topyright reserved

MA\ RKING GUIDELINE -B- T720(E)(A4)T INDUSTRIAL ELECTRONICS N3 QUESTION 9 o 1 ee a v Analogue Amplifier Schmitt Counter input — trigger signal Time Display base unit generator v { 9.2 The amplifier amplifies the analogue input signal. The Schmitt trigger converts i i i igi i i base generator an analogue input signal into a digital signal. The time produces a pulse which opens the AND gate for a fixed time. The jee gets allows the input signal to pass through. The counter counts the number o pulses allowed through the AND gate during a fixed time period. This count c appears on the display unit. tt TOTAL: = 10 Copyright reseekOWNIOaded from hlayiso.com

p080613) -3. H T710(E)(a1yT JECTION A QUESTION 1 4 Indicate been tbe following Statements are TRUE or FALSE. Choose the P . only ‘true’ or ‘false! f (1.1.1-1.1.5) in the ANSWER BOOK. se’ next to the question number ) 1.1.1 In a capacitor, the applied voltage leads the line current. 1.1.2 Light sensitive devices that i i oe radiate - Sinission davites light are known as photo ; 1.1.3 The algebraic sum of the voltages across the series components in i an alternating current Circuit is equal to the supply voltage. 1.1.4 The collector current of a transistor will increase when the base- emitter forward-bias voltage is increased. 1.1.5 An SCR has three junctions. (5 x 1) (5) 2 Various options are provided as possible answers to the following questions. Choose the answer and write only the letter (A-D) next to the question number (1.2.1-1.2.5) in the ANSWER BOOK. 1.2.1 Resonance can occur only in a circuit which contains we A_ resistance and capacitance. B_ resistance and inductance. C inductance and capacitance. D_ inductance only or capacitance only. 1.2.2 The main characteristics of an operational amplifier are ... Avery high output impedance, low input impedance, high voltage gain, ability to handle both AC and DC signals. B very high voltage gain, high input impedance, low output impedance, ability to handle both AC and DC signals. C very high voltage gain, high current gain, low output impedance, high input impedance D very high output impedance, high input impedance, high voltage gain, ability to handle both AC and DC signals. 2 1.2.3 Negative ions are atoms that ... Aare electrically neutral. B_ have lost an electron. C have gained an electron. D have lost a proton. ena Downloaded from hlayiso.com Please turn over jht reserved

T710(E\Ayy moeeets * pace ctance is WRONG: ing statement about rea 1.2.4 The following s atest _— i in a lagging Pn ; A An agers . resus siectron flow in an alternating UE B Reactance is resistan' t circuit. ; prplinn nce results in a I C Acapacitive reacta D Reactance is not influenced by the fi EC ading phase angle. pequency of the supply. _ is (are) exposed to light. 1.2.5 A phototransistor switches on when the .. A base-emitter junction B_ base-collector junction C_ base-emitter and base-co D base-emitter or base-collec Hector junctions junction tor jul (51) 1.3 Choose the correct word(s) from those given in ee WERE Gute the ' word(s) next to the question number (1.3.1-1.3.5) in . The (JFET/MOSFET) has its gate terminal insulated from the channel. 1.3.1 1.3.2 A common-emitter amplifier has a phase shift of (a) (0°/180°), a (b) (high/low) current gain and a (c) (high/low) voltage gain. ( 1.3.3 The output of a series clipper is measured across the (a) (diode/resistor) and the output of a parallel clipper is measured across the (b) (diode/resistor). ( 1.3.4 A (a) (dual beam/dual trace) oscilloscope has two electron guns and the (b) (dual beam/dual trace) oscilloscope has two modes of Operation. 1.3.5 Crystal transducers makes use of the (a) (photo-electric/piezo- 5 electric) effect and they develop a voltage across them when (b) (subjected to a force/exposed to light). : { TOTAL SECTION A: ) Downloaded from hlayiso.com ~ Copyright reserved |

3 8080613) “5. T7IO(E\(A1)T SECTION B QUESTION 2 2.1 f Ww ; yright reserved Study FIGURE 1 on the attached DIAGRAM SHEET and determine, with the aid of Kirchhoff's laws: 2.1.1 The equation for loop 1 (AFEDCBA). Set up the equation by Starting at point A and proceed in the direction of loop 1. 2.1.2 The equation for loop 2 (ADCBA). Set up the equation by starting at point A and proceed in the direction of loop 2. 2.1.3 The magnitude of the currents 7, and J, by making use of the equations in QUESTION 2.1.1 and QUESTION 2.1.2. The following paragraph explains the doping processes. Select the correct word from the options provided that would make the statements true. The deliberate addition of controlled amounts of foreign atoms or impurities to a pure or intrinsic semiconductor is called doping. If a (2.2.1 pentavalenttrivalent) impurity atom (5 valence electrons) was added, an excess of (2.2.2 holes/electrons) would be produced. This process is called (2.2.3 acceptor/donor) doping and results in (2.2.4 P-type/N-type) material being formed. In this type of material, the majority charge carriers are the (2.2.5 holes/electrons). However, if a (2.2.6 pentavalentftrivalent] atom (an atom that has 3 valence electrons) was added, an excess of (2.2.7 holes/electrons) will result and this process is called (2.2.8 acceptor/donor) doping. This process results in (2.2.9 P-type/N-type) material being formed. Here the majority charge carriers are (2.2.10 holes/electrons). Draw a labelled circuit diagram of a half-wave voltage doubler. JESTION 3 Consider the phasor diagram in FIGURE 2 on the attached DIAGRAM SHEET and determine the following: 3.1.1 The value of the inductor in mH 3.1.2 The value of the capacitor in uF 3.1.3 Supply current 3.1.4 Phase le wnloaded from hlayiso.com NOTE: The supply frequency is 50 Hz. (2) (4) (5) (3) [16] Please turn over

3.2 3.3 . dis Transients occur when an SCR is switched on and can have disastrous consequences for the circuit. Name the TWO methods used to eliminate transients. ; ee i RE 30 For full-wave control of a load a bridge circuit as shown in FIGU Nn the DIAGRAM SHEET can be used. 3.3.1 Redraw the bridge circuit of FIGURE 3 to show how it can be used to control an AC load. 3.3.2 Redraw the bridge circuit of FIGURE 3 to show how it can be used to control a DC load. QUESTION 4 4.1 4.2 4.3 Show, with aid of a labelled circuit diagram, how series-current negative feedback is achieved. The most important characteristic of a transistor when used as a switch is its Operating or switching speed. Refer to FIGURE 4 on the DIAGRAM SHEET and name each of the following: 4.2.1 t 4.2.2 to 4.2.3 te 4.2.4 ta 4.2.5 te 426 ft (6 x 1) Briefly describe the operation of each of the following amplifiers: 4.3.1 Class A 4.3.2 Class B Downloaded from hlayiso.com 08

(8080613) -7- T710(E)(A1)T i QUESTION 5 (6.1 Describe how a selenium photovoltaic cell is used as a transducer by providing the following: ' 5.1.1 A labelled sketch of the construction SAln2 The basic Principle of operation < 5.1.3 ONE area of application Name the FIVE groups into which transducers can be divided. Using the input waveform given in FIGURE 5 of DIAGRAM SHEET 1, draw the corresponding output waveforms for the following operational amplifiers (5.3.1-5.3.2) in the ANSWER BOOK. 5.3.1 Integrator 6.3.2 Differentiator JESTION 6 Draw a neat, labelled block diagram of a Successive-approximation digital voltmeter. Explain the purpose of a cathode-ray tube as used in an oscilloscope. Briefly explain the operating principle of the following diodes: 6.3.1 Varactor diode 6.3.2 Photodiode TOTAL SECTION B: GRAND TOTAL: Downloaded from hlayiso.com reserved (2) (2) [16] (3) [16} 80 100

(8080613) 308 DIAGRAM SHEET rT Rs B oO F Re lel: 1a Rg ; Loop 2 ak j a, |g 4 a "t = Loop 1 ae iv | : FIGURE 1 : Cc E D ° V+=100V. 50Hz FIGURE 3 1.=2.122A FIGURE 2 Base current { FIGURE 4 Downloaded from hlayiso.cohrUFE . ) Copyright reserved ;

MARKING GUIDELINE SECTION A QUESTION 1 Wa 1.4.1 1.1.2 1.1.3 1.1.4 1.1.5 1200 1.24 1.2.2 1.2.3 1.2.4 1.2.5 1300 1.3.1 1.3.2 1.3.3 1.3.4 1.3.5 Copyright resenE¥ownioaded from hlayiso.com 22. INDUSTRIAL ELECTRONICS N3 False True False True True BDo0ODO MOSFET (a) 180° (b) high (c) high (a) resistor (b) diode (a) dual beam (b) dual trace (a) piezo-electric (b) subjected to aforce 71 SLEVAIy \ (8x1) (5 x 1) TOTAL SECTION A: Please turn ové

T F IMARKING GUIDELINE 3. T710(E\(A1)T INDUSTRIAL ELECTRONICS N3 SECTION B (QUESTION 2 o1 0 2.4.4 Loop AFEDCBA 0=15(1, -1,)-151, = 151, ~151, -151,% = 15K = 30D | flv (2) (8 2.1.2 Loop ADCBA 105-101, -15T, bly [2]x2: -20 =-201, |) bly (2) f 2.1.3 (3]-i): -20 =-351, W ( I, =0,571AW { A Substitute 1 = 0,571 A in [2]. ( ~10 =-10(0,571)-151, =~-5,71-151, W (2 -4,29 = -151, d I, =+0,286A W (4) 2 2.2 2.2.1 pentavalent 2 2.2.2 electrons | 223 donor 2.2.4 N-type 2.2.5 electrons 2.2.6 trivalent 2.2.7 holes 2.2.8 acceptor 2.2.9 P-type 2A holes (10x%) (5) (A) (A) 2Vmn (4) layiso.com 6x1) 3) [16}

MARKING GUIDELINE INDUSTR QUESTION 3 3.4 3.1.4 a Xa 7 = 108. ~ 2.122 = 47,125 2 il 3.1.2 v Xe = € Le 100 ~ 3,14 =318472 0 3.1.3 I, =Vi+(e hy = 2? +142 -2,122) ¥ =2,245AS 3.1.4 I Cos@ = T, ae 2.245 =0.391 % 3.2 3.3 LC filters, Zener diodes, Tranzorps, Varistors 3.3.4 aaa ©) epyright reseveq Downloaded from hlayiso.com JAL ELECTRON RK = on _ Ame. ov 2xmx50 =150mH v 1 Xe = aC 1 Css 2AfX,, = 3yx50x31847 ¥ =100 uF 6 = Cos 0,891 = 27,010° y OR (Any 2 x 4) v Please turn |

fARKING GUIDELINE INDUSTRIAL Er; 332 RIAL ELECTRONICS N3 : Oo <M © y (2) T710(E)(A4 \T [16] JUESTION 4 A =v = (6) 4.2.4 Delay time 4.2.2 Rise time 4.2.3 Turn-on-time 4.2.4 Storage time 4.2.5 Fall time 4.2.6 Turn-off time (6 x 1) (6) 4.3.1 In Class-A amplifiers the bias point corresponds to the mid-point of the active regiony of the characteristic curve and is selected so that the current flows during the whole of the input cyclev’. (2) 4.3.2 In Class-B amplifiers the bias point corresponds to the cut-off region” of the characteristic curve and the current flows only during the positive half-cycles of the signal voltagev’. (2) [16] Downloaded from hlayiso.com,, 6. smn over ht reserved

re MARKING G -6- THO) VIDELINE INDUSTRIAL ELECTRONICS N3 CEVA, aRKIt QUESTION 5 54 5.4.4 eee ERODES UES | [user hid 1 GOLD SELENIUM DEPOSIT ON METAL BASE Drawing = 2 marks Labels = 2 marks ( 5.1.2 A voltage is generated in a semiconductor junction device ~ when incident light activates the cell”. 5.1.3 Light intensity OR Solar energy 5.2 e Resistive e Capacitive ? e Inductive e Photo-sensitive e Piezo-electric 5 53 6.31 §.32 Vin Vin Vo Vo i Copyright reserved Downloaded from hlayiso.com (2x2) Please turn ov

RKING GUIDELINE T710(E)(A1)T = A INDUSTRIAL ELECTRONICS N3 pUESTION 6 logic 4 programmer, save |v, | clear v analog unknown — voltage Ve % register MY reference voltage 7 source eBEREED] display |% Labels = 7x/4 = 3% Drawing = 7x/AZ= 3% Correctness= 1 (8) The cathode-ray tube (CRT) produces a sharply focused beam of electrons ” and accelerates it toa very high velocity to strike the fluorescent screen with enough energy to light up in a small spot. ¥ (2) 6.3.1 In a PN-junction diode, the depletion region forms part of the dielectric. ¥ By adjusting the reverse bias voltage ¥ the depletion region widens or narrows moving the electrodes further apart or closer, certain specific values of junction capacitance can be controlled “, so that the diode can be used as a capacitor. (3) 6.3.2 When light falls on the PN-junction, “electron-hole pairs are created which increases the availability of minority carriers. The minority carriers under reverse-bias conditions cause an increase V in the leakage current. As the light intensity increases, the leakage current increases VY and the diode becomes more i conductive. (3) fe [16] TOTAL SECTION B: 80 GRAND TOTAL: 100 Downloaded from hlayiso.com Tight reserved

Indicate whether the following Statements are TRUE or FALSE. Choose the answer and write Only ‘true: F ; ; (1.1.1-1.1.10) in the ANSWER Boy 8° next to the question number 111 Kirchoffs laws are applied to DC circuits. 1.1.2 Kirchoff's Second law refers to current 1.1.3 The re . . . . frequency. Of a capacitor increases with an increase in 1.1.4 The impedance of a par on ., all resonance. p el RLC circuit is at a minimum at 1.1.5 Elements with less than four valence electrons are called resistors. 1.1.6 The resistance of a pn-junction diode is high when the diode is forward biased. de dail LED's are used in Seven-segment displays to form the segments. 1.1.8 The application of a transistor as a switch is a manual operation. 1.1.9 Gross errors in measuring instruments are also referred to as human errors. 1.1.10 An SCR isa four-layer semiconductor device. (10x14) (10) Choose the correct word or words from those given in brackets. Write only the word or words next to the question number (1.2.1-1.2.10) in the ANSWER BOOK. 1.2.4 The main advantage of an SCR is that it has a (high/low) control power. 1.2.2 Negative feedback is a process used to improve the performance of a circuit by (increasing/reducing) its gain. Transition capacitance is due to the charge which exists in the (23 depletion layer under a (forward/reverse) bias condition in a pn- diode. 1.2.4 The impedance of a parallel resonant circuit is at its (minimum/maximum) value. 125 An osciloagrray Af RUE FrOiN Hidyiso'@Ent’ (current/vo! Please tum over ht reserved

(8080613) -4- T77O(E Vay 08! 1.2.6 The resistance of an NTC thermistor is (directly/inversely) proportional to temperature. qui 1.2.7 When both inputs of an operational amplifier are equal, the output iy will be (one/zero). 1.2.8 (Line/Forced) commutation is applied in SCR's when an AC supply is used. 129 Open loop refers to a system whose output is (monitored/- unmonitored). 1.2.10 (Kirchhoff's/Ohm's) law states that the current entering a point equals the sum of the currents leaving that point. (10 x 1) ri 2 TOTAL SECTION A: F SECTION B QUESTION 2 Study FIGURE 1 below and calculate the value of the current Iz in the circuit, by making use of Kirchoff's laws. a hu 88 Bb 42 c > _ ae ~ y Is 2 — 80 30 NE 12V ! E D 70 59 FIGURE 1 Spynontreserved ~~ Downloaded from hlayiso.com Pyr Please tum ovel

-5- T770(E)(M28)T 120 V/ | 1 50 Hz | Pl a FIGURE 2 Calculate the following from the circuit: 3.1.1 The total current of the circuit (3) 3.1.2 The phase angle 8 (2) 3.1.3 The capacitance of the capacitor in uF (4) 3.1.4 The inductance of the inductor in mH (4) 3.1.5 The resistance value of the resistor (2) 52 Draw the phasor diagram of the circuit in FIGURE 2. ray QUESTION 4 4 Briefly describe the process of acceptor doping as applied to atomic theory. (4) Make a neat, labelled sketch to indicate the width of the energy gap of an a insulator material. Describe the operation of a negative shunt clipper when the positive signal is 3 applied to the circuit. rib Downloaded from hlayiso.com Please turn over

EL, alll (8080613) 6 T7TOLE M29), i08t QUESTION 5 : wncdi th uk ail Draw a neat circuit of a shunt positive clipper and indicate Ine output waveform if an AC signal is applied on the input. ( 5.2 State the mode of bias in which a varactor diode conducts. ' 5.3 State the type of diode that you would use to keep the output voltage stable and regulated. e to bias the diode in QUESTION 5.3 above 3 5.4 State the mode that you would us to obtain a constant voltage on the output. { 5.5 Draw a neat circuit using the diode in QUESTION 5.3 which will ensure a regulated and stable output voltage. QUESTION 6 6.1 State FOUR advantages of negative feedback as used with amplifiers. 6.2 Draw a neat circuit diagram of a series voltage regulator which uses an NPN transistor and a Zener diode. 6.3 Explain how an SCR can be turned on by applying a breakover voltage switching-on method. Downloaded from hlayiso.com

uesTION 7 Briefly describe how an Ke 4 “filter method is used to suppress transients in SCR's. - a neat circuit whi . 2 Oe an NPN transistor ie be use to switch off an SCR. The circuit must point of an SCR. will reduce the current to be below the holding ZT B Study FIGURE 3 below and answer the questions. Vi Voutput FIGURE 3 State the type of output expected in each of the following cases: 7.3.1 If V1 is greater than V2 7.3.2 If V2 is greater than V; : 7.3.3 If V; equals V2 (3 * 2) (6) | [12] Downloaded from hlayiso.com Please turn over yright reserved

ee 1770 (80806 8 sy 1 8 3) p80¢ QUEST . ION 8 citance of 4 capacitor. Refer tg «Dt The type of dielectric material can affect tne cape questions with reference tg a FIGURE 4a and FIGURE 4b below an Capacitive transducers. — re Level of liquids _ N, te? Capacitor fully immersed in liquid Capacitor plates out of the liquid FIGURE 4a FIGURE 4b L 8.1 Explain the effect which the level of the liquid in FIGURE 4a will Nave towards the capacitance of the capacitor. 8.2 Explain the effect which the level of the liquid in FIGURE 4b will have towards the capacitance of the capacitor. (2 2) QUESTION 9 An AC waveform is displayed on the screen of an oscilloscope and it shows that it fits into eight blocks from the positive peak to the negative peak. One cycle of this waveform is completed to fit into six blocks horizontally. The peak-to-peak voltage and the period of the waveform are 1,6 V and 60 ps respectively. Calculate the following: 9.1 The volts/div setting of the oscilloscope 9.2 The time/div setting of the oscilloscope 9.3 The RMS value of the waveform (3 x 2) TOTAL SECTION B: GRAND TOTAL: Copyright resedOWNIoaded from hlayiso.com

- MARKING SUIDELINE QUESTION 1 141 wre 1 1 1 1 16 1 ' 1 1 1 JPN NM BD *) Do EC cS .N3 INDUSTRIAL ELECTRONICS True False False False False False True False True voitag if rsely Ze Line unmonitored Kirchoff's TT 5, t OE) Mg, ar gC Fed TOTAL SECTION A Downloaded from hlayiso.com Copynght reserved o Dinesew ttt

ING GUIDELINE 3 MARK ' INDUSTRIAL ELECTRONICS N3 TTTOKE) A426) iF UESTION 2 ; Co Minimise the currents in the circuit: Is = (ly - Ip) i Loop ABEFA 42 =6 |; + B(ly-l2) + 21, (8 1G ly le ereeceyerwiicennneenerarrennsd () v v Loop BCDEB (Any other loops can be used) | 0=4l2+3 l2+5 le—8(h — Io) O == BI + 20 doesent een 0) voy (2) «2:0= 164 +401 scceeaseee Q v 12=161,-8 lo. Se creer " v | 2 = 2 42 = 16 lh — 8(0,375) ——— a aed 1, = 0,938 A 4 Current I3 = (4 — 2) Therefore |3 = (0,938 — 0,375) lb = 0,563 A vv 110} Downloaded from hlayiso.com Pfeesesum Ever opyright reserved

MARKING GUIDELINE QUESTION 3 3.1 3.4.4 3.1.3 3.1.4 3.1.5 -4- INDUSTRIAL ELECTRONICS N3 Z l= In2 + (Ico — Ib) = [52 +(3,5-28" “ ~ I= 5,049 A v L Tan 9 == IR _ 120 v 23,142 XS50X34,286 C = 92,828 uF _ 120 28 X=428560, % And therefore: X= 2xtrxfxL 42,856 Y 2x3,142x50 L= 136,397 mH. ¥ Downloaded from hlayiso.com a. TTTOLE) M29), . (Or any other applicable way) h ee

& GUIDELINE aKING ~5- Fs INDUSTRIAL ELECTRONICS N3 3.2 1-=3,5 A w — (Ie-lL) r=5049AQ y (3! > IR=5A i [L=2,8 Av , (3) @ [13] : | QUESTION 4 (44 As soon as a pentavalent atom (atom with 5 valence electrons) is added I into silicon” or germanium (atom with 4 valence electrons), covalent ron is left¥ bonding takes place between adjacent electrons but one elect unbounded; as soon as this free electron is lost to other atoms a hole is created in the pure material.” These holes are able to attract electrons and are therefore referred to as acceptor doping. ~ (4) ( 4.2 Large energy gap vy Valence Band v (3) 4.3 When the positive” signal is applied into the circuit the diode becomes , reverseY biased. During this time there is no current flow through the my diode and therefore the output voltage equals the input voltage. tot Downloaded from hlayiso.com

TTTO(E\(M28)y i MARK 6 aril ING GUIDELINE INDUSTRIAL ELECTRONICS N3 M QUESTION 5 ques 54 6.1 v v ; Vi v ‘ ov > 5.2 (3) (1) 5.2 Reverse bias . (1) 5.3 Zener diode 4 5.4 Reverse bias (1) 5.5 Re Is | i_* 3.3 Y iz Yok v |_| Vin 7 i Vo ioe R v a WE (3) 1 [9] 2 B Downloaded from hlayiso.com Copyright reserved "py Dinnee turn nvel

r MARKING GUIDELINE -7- | INDUSTRIAL ELECTRONICS N3 T7046 E QUESTION 6 M2a)t Improves Stability of the Circuit. Reduces its gain. Increases its Operating bandwidth. Reduces distortion, Reduces noise. VV VVV Vv Increases the input impedance and reduces the output impedance. (Any 4 x 1) (4) j (4) In the absence of the gate current, the anode to cathode voltage is increased to the extent that the breakovery voltage of the SCR is reached. An avalanche breakdown occurs and the SCR switches on by a regenerative process, ” (3) [11] ESTION 7 L-C filters reduce the effect of the transient by means of smoothing. ~ The capacitor is used to smooth the voltage” while the inductor is used to suppress the change in current.” (3) la lH - v Ic —_ v v y L 6 7.3.1 The output will be negative. 7.3.2 The output will be positive. a 7.3.3 The output will be zero, Pa Saroaie (6) S\\ a Ay ne” ‘\ e Downloaded frogrhlayiso.com ht reserved Please turn over

MA RKING SUIDEUNE 5N3 -8- Ic: INDUSTRIAL ELECTRON a since both plates The capacitance will increase ‘ ial between The liquid acts as a dielectric material be’ r will decrease since both plates are remo oO ” 7s Capaetaniee Ghee serves as a dielectric material.” from the liquid material” which QUESTION 9 94 Ve-p)= number of vertical divisions * Vidiv Vidiy = —_—¥@=P)__ number ofdivisions v Vidiv = +2 8 Vidiv=02V . Midiv=0,2V_ 9.2 T = number of horizontal divisions x Udiv tdiv = ul number of divisions . 60 x107§ tdiv Sain Lvislons v tidiv = 10 us Vems== x0,707 ¥ Vams=0,566V_ a are immersed in the liquig. the plates of the capacitor v v Veq (3 x 2) TOTAL SECTION 8: GRAND TOTAL: Downloaded from hlayiso.com Copyright reserved TNT ATTN AATTTNRTT,

(go80s! 3) fis SECTION A QUESTION 1 T6S0(E)(J25)7 eRe; = Indicate whether the fol llowin statemen answer and write only tres ts are TRUE or FALSE. Choose the Or ‘false’ i (1.4.4-1.1.10) in the ANSWER BOOK. next to the question number = = om E Bipolar transistors are current-operated devices E 1.1.2 In a series RLC circuit the impedance at resonance is a maximum F 1.1.3 The Output from a negative series clipper consists only of the : Positive half of the input signal. : 1.1.4 Standard-type Oscilloscopes can measure voltage, current and E resistance. F 1.1.5 The parallax error is @ gross error. [ 1.1.6 Current can flow through a Zener diode in both directions. f 1.1.7 A silicon-controlled rectifier can be switched off only by removing the gate current. An operational amplifier has a high output impedance, Digital variables change continuously with time. An electron has a nei gative charge of approximately 1,602 x 10" ¢ coulombs, (10x14) (10) Downloaded from hlayiso.com Please turn over

(8080613) 1.2 Various options are Choose the answer and write only the letter T690(E)(J25)T -4- given as possible answers to the following questions. next to the question (A-C) number (1.2.1-1.2.10) in the ANSWER BOOK. 1.2.1 1.2.2 1.2.3 1.2.4 a eae In a parallel resonant circuit, the following conditions exist: A. Zisamaximum, | is a maximum B Zisamaximum, | is a minimum C Zisaminimum, | is a maximum rom the on-state The maximum time taken for the diode to switch f to the off-state is called the ... A duty cycle. B fall time. C_ reverse recovery time. ectrons that pentavalent atoms have in their outer The number of el shell are ... Owyr ak w The following diodes are normally used in the reverse-bias condition: A pn-junction, Zener, varactor B_ photo diode, Zener, varactor C_ pn-junction, photo diode, Zener A transistor has an emitter current of 22 mA and a collector current of 21 mA. The base current is ... A 43mA. B 1mA. C 22 mA. © The forbidden energy gap for a semiconductor is ... A small. B large. C_ non-existent. Downloaded from hlayiso.com fay [7

0800!) T690(E)(J25)T 4.2.7 The transducer u idgi structures is Sed to measure the force applied to bridging A wheatstone bridge. B linear variable Giff i © strain Gauge erential transformer. 42.8 The operational ampilifi the ... r whose gain is always more than one is A inverting amplifier, B non-inverting amplifier. C voltage follower, 1.2.9 One section of the hori is the ... izontal-deflection system of an oscilloscope A probe. B_ input attenuator. C_ time-base generator. 1.2.10 | The nearest an instrument reading will reach the true value of the quantity being measured is called the ... A accuracy. B precision. C_ resolution. (10x1) (10) TOTAL SECTION A: 20 Downloaded from hlayiso.com Please tum over Copyright reserved

I —————— ¥ T69 O(e tp * 8) (8080613) SECTION B QUESTION 2 M SHE 2.1 Study FIGURE 1 on the attached DIAGRA aid of Kirchhoff's laws: «up the aereceniae a i 1 (ABCDA). Se ick arrow), an tip Sed eee Ne direction of loop 1 (thick ) at poi ET and determine, with the CDEFABC). Set up the equation by 2.1.2 The equation for loop 2 ( eed in the direction of loop 2 (thick starting at point C and proc arrow). ing use of The magnitude of the currents /, and /, by making the 2.1.3 equations in QUESTION 2.1.1 and QUESTION 2.1.2. 2.2 An SCR can be controlled by making use of four teil anode Nate following statements are descriptions or definitions of the : the method that best describes the given statement. 2.2.1 This method of control is used when the SCR performs simple switching. 2.2.2 This method of control is a combination of phase and cycle control. 2.2.3 This method of control is achieved by controlling the time at which the gate of the SCR is triggered. 2.2.4 This method of control is achieved by switching the control device on for a number of full cycles and then switching the control device off for a number of full cycles. (4x 1) 2.3 Show by means of a labelled circuit diagram how two SCRs connected to form a SCR-diode bridge can be used for F ULL-WAVE control. Downloaded from hlayiso.com Copyright reserved ( {i

080! 3} | -7- | : T690(E)(J25)T Question 3 : A series Circuit Consists of a, ; af acitor of 100 oF an induct 4 cap MF Connecteg acrose mata resistance of 12 ohms and a calculate the: 90 Hz supply. 3.1.1 Impedance 3.1.2 Current (3) 3.1.3 Voltage across R . (2) 3.1.4 Voltage across L ; (1) 3.1.5 Voltage across C . (1) 3.1.6 phase a ngle between the current and the supply voltage (2) Draw neat, labelled Circuit 2 follwing inodes: diagrams of an Operational amplifier used in the 3.2.1 Summing } 3.2.2 Integrator (2 x 3) (6) [16] UESTION 4 Draw a neat, labelled circuit diagram of a push-pull amplifier. Indicate on the circuit ALL relevant waveforms and bias polarities. (7) 1 Draw a labelled output-characteristic curve of a COMMON EMITTER amplifier. On the curve draw a loadline and indicate where you would place the Q-point on the load line for a class-C amplifier. (4) The following paragraph explains the operation of a phototransistor. Complete the paragraph by making use of the words provided in the list below. (NOTE: A word may be used more than once.) Write only the word next to the question number (4.3.1—4.3.5) in the ANSWER BOOK. i . regi 13.2) ... leakage The light that shines on the (4.3.1) ... region causes (4 : cupart to flow. This, in effect, is a withdrawal of (4.3.3) ... from the base, © which j i . A(n) (4.3.4) ... in the light which is necessary to turn the transistor on. | intensity would correspond with a(n) (4.3.5) ... in base current and a larger | increase in the collector current. | Poles electrons’ reverse; forward; decrease; increase; collector-base: emitter-base hlspytom (5) Saded Tea [16] wore eg cet Go good "aa gare 3 ak

(808061 3) QUESTION 5 RAM SHEET to answer the Sf Refer to FIGURE 2 on the attached DIAG questions below. 5.1.1 Identify the transducer’ FIGURE sive ato d given!" ting princip! ey 3 seth be explanation of its operating 5.1.4 Name TWO areas of application. ical) properties of atoms i nd chem i Select the ine the electrical (a 4 four points. ct the 5.2 Valence electrons determin sed in the following fo. See eould makes These properties are summatt ae correct statements from the option statement true. ith [(a) less/more] than four valence ts wi F ; oat ee Tee eerete [(b) give up/tend fo acquire (gain)] one elec 7 or more electrons. : s/more] than four valence i lements that have [(a)/ess/ ! 828 fens and [(b) give up/tend to acquire (gain)] one or more electrons. 5.2.3 Insulators are atoms with exactly [(a) eight/four] valence electrons. They [(b) neither lose nor gain/share] electrons. i tly [(a) eight/four| 5.2.4 Semiconductors are atoms that have exac valence electrons. They [(b) neither lose nor gain/share] Mae x 2) QUESTION 6 6.1 With reference to an oscilloscope describe the purpose of the following: 6.154, Deflection plates 6.1.2 Delay line : (2x2) ee Draw a labelled block diagram of a continuous-balance digital voltmeter. (Use rovided in braci arrows to indicate data flow). 6.3 Name FIVE characteristics of Operational amplifiers Copyright reserveg ( ti TOTAL SECTION B: Downloaded from hlayiso.com GRAND TOTAL:

T690(E)(J25)T q Sel 12v FIGURE 1 a SSS Leena | FIGURE 2 Downloaded from hlayiso.com

MARKING GUIDELINE SECTION A QUESTION 1 Ved 1.2 — = Pas aan nw. ON OO A WI co) ° 1.2.1 1.2.2 1.2.3 1.2.4 1.2.5 1.26 1.2.7 1.2.8 1.2.9 1.2.10 -2- N3 INDUSTRIAL ELECTRONICS True False True False True True False False False True ‘oss FORO>DMOOW (10 x 1) TOTAL SECTION a: Downloaded from hlayiso.com aa (¢

| aKING GUIDELINE Ma ti 3. NDUSTRiAaL ELECTRONICS N3 T690(E)(J25)T gecTION B uESTION 2 { 2.1.1 Loop ABCDA 2 For loop we have: 12531, + 3LkVv vv 2.1.2 Loop CDEFABC 2s 3h 2+7\h-b)+3hv OR 42 = 2h —b) +7 (h —b) + ia 14 “Sh + 3h 12 =2h~2b+7h-7b+3h a. aha Sk 12 = 12h, -9 A BR ay (2) 2.1.3 1]- [2]: = [1 [2] 16= 71, ¥ OR 14:48 = 121, +121, . v “hh =22A4 1-2 :36=211, ; “1, =L714A Substitute 1=2,2A in [1] Subl,.in equi: 12= 352.2 + 3h, 12= 3, + 3(1714) 3lz =12 -6.6 6,858 = 31, \ b= 1,8A% “1, = 2,286.4 (4) | Yi 2.2.1 Static control ~ 2.2.2 Cyclotronic control” 22.3 Phase control v 2.2.4 Cycle control ¥ (4) al} — A SCR, D, A “ ‘ A * “ correctness AD Control circuit x A SCR; D2 —_+e : orrectness (ONE mark for diagram and THREE marks for c ) ' te Downloaded from hlayiso.comPease tum over | ight reserved

SMIVELINE INDUSTRIAL ELECTRONICS QUESTION 3 3.4 3.4.4 X, =2nfL =2x71x50x0,5 =157,0802 -J! © 2nfC 1 ~ 2xnx50% 100% 10° = 318310 Z= RK? +(X, -X,) = yfl2? + (157,080 - 31,831) v =125,823Q v 3.12 I-t- at =1748A ¥ 3.1.3 V, =IxR =1,748x12=20976V Vv 3.1.4 V, =IxX, =1,748x157,080 = 274,576V 3.1.5 Vo =IxX¢ =1,748x31831=55,641V 3.1.6 V, 20,976 “a 8 =Cos '} ® |= Cos || 20976) 9, oan =Cos 1 ® [? 270 923" ORO=Cos 5 2 =Cos ! 1? 125,847 v = 84,5490 32 3.24 R, R, “i R1,R2,R3 andRi=1 v v,_,-& Correct connections = iv 7 Correctness = 4 wv Vs Vo Copyright reseryeq DOWNloaded from hlayiso.com 1 Please tum ove 8 t

6 GUIDELINE at! INDUSTR oo AL ELECTR 2: ‘ONI 3 CS N3 TO8O(E), 25) Rtandci=1 ¥ om connections y rr ectness v (3) {16} A | us | f Vour i i | Correctness = 1 mark (7) a Placing Q in int = z % mate , re = 1 mark Drawing load line = 1 mark lg (mA) cn = Ip, le Vce and drawing c.c 5,0F 45) ipo=450pA 40 \pe=400HA 3,5] Ip7=350HA 3,0+ r lee=300UA 25 Ips=250NA 20 lae=200HA a+ leg=150yA 4, 4— Ip=100uA 05 \as=SONA ) , ; , A S 10 15 25 Vce(V) v (4) Downloaded from hlayiso.com Please turn over Copyright reserved

TE9O(E)(J25)7 M, IARKING GUIDELINE aECTRONICS N3 L 43 INDUSTRIA ; 4.3.1 collector-base 43.2 reverse | 4.3.3 electrons \ 4.3.4 increase (5) 4 4.3.5 increase 16] QUESTION 5 | 5.1 5.1.1 LVDT v A 5.1.2 (a) — supply (b) movement (c) core % (dq) output A n externally applied force varies 5.1.3 Positioning the magnetic core throu han exter former. Th F F windings of a transformer. The the difference in voltage of two secondary evi: diedion ard Magnitude of this difference is an indication _O' magnitude of the applied force. (3) 5.1.4 Pressure - force measurements ¥ Displacement — linear motion-magnitude of movements Position - to indicate direction of applied pressure or motion (Any2x1) (2) | 5.2 5.2.1 (a) less ¥ (b) giveup . §.2.2 (a) more/ (b) tend to acquire (gain) ¥ 5.2.3 (a) eight¥ (0) neither lose nor gain y | 5.2.4 (a) four’ (b) share v (4x2) (8) [16] Downloaded from hlayiso.com Copyright reserved

akiING GUIDELINE AN -7- INDUSTRIAL ELECTRONICS N3 T69O(E)(25)T Al 6.1.1 Deflection plates Position the CRT Simultaneous application of Spot anywhere on the screen by voltage inputs. v appropriate vertical and horizontal 6.1.2 Delay line delays thé arrj ; ; deflection pletes © arrival of the input waveform at the vertical S until the TRIGGER and TIME BASE circuits have had a chance to start the sweep of the beam. / (2 2) (4) 6.2 reset analog unknown = Vf A voltage au adda “4 & comparator counter display £ a ATA A V2 A A clock A DA OA converter (7) 63 High input impedance¥” Low output impedance” High voltage gain” Wide bandwidth” Its parameters are matched and track well with temperature changes” Can handle both AC and DC signals (5) [16] TOTAL SECTIONB: 80 ) GRAND TOTAL: 100 ] Copyright reserved Downloaded from hlayiso.com Seat nnn" chee ape mmuatcateaticad cS ANLASE algae et xc crete ee

1.2 (3) ] 1202 Consider the given information and use Kirchhoff's laws to calculate the value of the current flow through each resistor. (10) [13] ~ QUESTION 2 2.1 Alternating current produces a reaction within various components in order to produce the required output. Define the following terms with reference to alternating current circuits: 2.1.1 Inductive reactance 2.1.2 Impedance (2 x 2) (4) Downloaded from hlayiso.com copyright reserved Please turn over

T7808) 4, y (808061 3) -4- 3) ; (i ; f 10 P internal resistance o ohms , il of 0,5 H with an connected acro, 22 Asetigs LO cireuil ae 2 — es components ae BO hort oS an ; ; ; 4 . Sharnating boscher shine of 240 volts with a Ireg tions: " llowing questions: Consider the given information and answer the fo labelled sketch of the ett and draw a dotted block to 2.2.4 Make a label , il. show the internal resistance of the co! ty 2.2.2 Calculate the impedance of the coil. ty ite the total impedance of the circul a | 2.2.3 Calcula' 2. jate the current flow through the circuit. @ | 2.4 Calcul. i voltage across | 2.2.5 Calculate the voltage across the coil and the 9 he | capacitor. (4) {17 QUESTION 3 | 3.1 Atomic theory provides information on the movement of electrons that Produces electric current. Indicate the number of each of the valence electrons that are found in the atoms of the following components: : 34 Insulators | 3.1.2 Semiconductors 4: (2*1) Q 3.2 Draw a circuit diagram of a series negative clipper. Clearly show the 4. alternating Current input and Output. (3) 4. 3.3 Explain the process that Produced the output for the circuit in QUESTION 3.2 Clogs 3.4 Make a neat, labelled Sketch that shows the forward and reverse | AE characteristics of a zener diode. (4) (1) Downloaded from hlayiso.com Copyright reserved Co Please turn ovel

4.2 4.3 4.4 4.5 46 Copyright reserved Base Current From the grap 80 micro-amps, h, determine the Output current when the input current is State the type of amplifier that the graph represents. Indicate the type of class that the amplifier uses in its operation. State FOUR advantages of a field-effect transistor. Negative feedback stabilises the gain of an amplifier. Draw a block diagram that represents the concept of negative feedback. Downloaded from hlayiso.com (1) (1) (1) (1) (4) [12] Please turn a

Scription from COLUMN B that a ) Next to the question number (5. i a 79016), ; UMN A. Write 9 | aterm in COL nly n) in the ANSWER BOOK. COLUMN B — quired to keep an SCR in @ conducting re state dds two or more inputs for Switching a purposes voltage controlled transistor various electronic ice that uses riou sarponents for various switching purposes method used to switch off an SCR produces an output that is in phase to the A137 input (808064 3) QUESTion 5 Choose a de. the letter (A-F Speen eee Ks COLUMN'A 5.1 Forced commutation 5.2 Non-inverting operational amplifier 5.3 Holding current 5.4 Operational amplifier 5.5 Summing amplifier 5.6 FET QUESTION 6 6.1 6.2 6.3 6.4 (6 x 4) Draw a diagram of a capacitive transducer that is used to measure pressure, Explain the principle of Operation of the device drawn in QUESTION 6.1. List THREE factors to consider when selecting a transducer. Name TWO types of errors that may occur in measuring instruments. 65 State the causes of the errors in QUESTION 6.4. 6.6 Make a labelled sketch of a selenium photovoltaic cell, 6.7 Explain the operation of the selenium photovoltaic cell. Downloaded from hlayiso.com Copyright reserved Please tum ovel ( 6) 0) (3 Q) Q ) Q) (2 Cc

[6] 0808" 3) T780(E\Ata)T quest iON 7 Draw a labelled block qj 4 for inding in goo am Of a ca F used for fault finding in electronic devices "tty Oscilloscope that may be 72 Explain the function of the Cathode-ray tube 13 Make a labelled sketch of a Saw-tooth waveform 4 Explain the difference bety ; 1 oscilloscope. en a dual-trace oscilloscope and a dual-beam TOTAL: Downloaded from hlayiso.com (4) [19] 100

M ARKING GUIDELINE Qe INDUSTRIAL ELECTRONICS N3 QUESTION 4 14 1.2 Ik +0,.2=03+0,15 VY k= 0,45 —0,2 k=O025Av IR, = 1 IR3 = lp IR2 F— Fy — lo 1221 412.) ONY 12= 1h + 4, - 4h vv 36 = 151,12 v 12 = 1h +12, 48 = 161, h=3A v 12 = 5h — 4I 12=5x3-4bv 4 =3 b=0,75A v h-~bk=225A v Students may also use loop : 0 = A(ly — Ia) + 12 Ie Copyright reserved Downloaded from hlayiso.com Tr EVA, Q (2) Qo (t [13 A Please turn ove!

yaRKING GUIDELINE & QUESTION 2 INDUSTRIAL ELECTRONICS Ng 24 2.1.1 The o Reson the flow of current through a Coil in an AC circuit 2.1.2 22 2.2.4 Vs =240V , 50Hz Half mark per component; Vs = half mark (2) 2.22 X= 2xm* 50 «0,5 = 157,080 v Z.= 107+ 15708 Vv = 157,398 Q v (3) = 31,831 0 v Z= \/[10? + (157,08 — 31,831)2] 4 = 125,648 0 A 2) 224 = 240/125648 v =191A v (2) 22.5 Vc=1,91% 31,831 “=60,797V Vv Vi = 1,91 x 157,398 ¥ =300630V v , {a Downloaded from hlayiso.com Copyright reserved Please turn over

T790(E Kara), MARKING GUIDELINE 4. SN3 INDUSTRIAL ELECTRONIC QUEsTion 3 81844 Bight 3.1.2 Four (2 1) 0 3.2 A | a v A Input ‘S Output ¥ Circuit Waveforms Circuit — 1 mark; waveforms — 2 marks (3) 3.3 The positive half-cycle conducts through the forward-biased diode, Producing a positive half-cycle at the output. ¥ The negative half-cycle is blocked due to the diode being reversed biased ~ (2) 3.4 A Ip (mA) 201. 15|. A Vy 10} Forward bias a 5 ei 6 4 2 0] J 2 4 ea A Reverse {a 1s bias A i ‘ 4-10 B 4-15 Ir (md) y (4) (11] Copyright reserved Downloaded from hlayiso.com Please tum over

akING GUIDELINE NA -5- INDUSTRIAL ELECTRONICS N3 1790(E)(A13)T quesTION 4 4) BO HA (1) W 50 mA (1) 43 Common emitter amplifier (1) 44 Class A (1) 45 ¢ High input impedance ¢ Small gain bandwidth ¢ Good thermal Stability * Relatively unaffected by radiation * No offset voltage when Used as a switch 4 e Less noisy than bipolar transistor ANY 22 1) i 46 v Source Amplifier Output Vv @) v Feedback iti {B) Diagram — 2 marks, labels — 2 marks ae QUESTION 5 5.1 E 5.2 F 5.3 A 5.4 D 5.5 B 5.6 Cc (6 x 1) [6] iso.com Downloaded from hlayiso.co Copyright reserved Please turn over

(6¢@¢«c:U T790(E\(A} aT -6- MARKING GUIDELINE INDUSTRIAL ELECTRONICS N3 QUESTION 6 LECTRIC 64 bm! —_ FIXE r FLEXIBLE v METAL DIAPHRAGM J v PIN > — Diagram — 3 marks; labels — 2 marks i roduces movement between the * aeeloneed Reed plaeay HUE ee a corresponding change in capacitance (3 x bold text The accuracy required 6.3 e e Physical quantity to be measured e The availability for replacement ; — ; ¢ The suitability to the type of measurement/converting principle that is most suitable e The type of supply — ac or de ¢ The environmental conditions (Any 3 x 1) 6.4 ¢ Systematic e Environmental e Gross « Random (Any 2 x 1) 65 e Systematic errors — due to friction of bearings and faults with the spring. e Environmental errors — factors due to magnetic or electrostatic fields, temperature and humidity and barometric pressure. e Gross — errors due to human inability in reading accurately or inability to use the instrument as required. ¢ Random errors — factors that are unknown. (Any 2 * 1) Downloaded from hlayiso.com Copyright reserved 4 (5) (3) (3) (2) (2)

aiNG GUIDELINE ne 7. INDUSTRIAL ELECTRONIcg N3 T790(E)(A13)T Solar or other illumination v v glass caver Sheet Selenium deposit on Metal sheet or foil v ' (potential difference) 3 marks - diagram; 2 marks — labels (5) 67 The photovoltaic cell has various i ications of sunlight to electricity. materials that convert application 2) [22] QUESTION 7 Al v v VERTICAL | DELAY AMPLIFIER [ UNE LUMINOUS ELECTRON Sno GUN TOCRT rv v G>--f-a--- Hy SUPPLY | UY SUPPLY \ ! A TO ALL CIRCUITS VERTICAL DEFLECTION PLATES a SCREEN v £LECTRON BEAM HORIZONTAL DEFLECTION PLATES v v v Ly TRIGGER TIME BASE HORIZONTAL CIRCUIT GENERATOR AMPLIFIER . CRT does not need to be in diagram (10) 7.2 The cathode-ray tube is a vacuum tube that uses one or two electron guns to accelerate and deflect the electron beami/s to Produce images, for example waveforms. (2) h Downloaded from hlayiso.com A, -Copyright reserved

“ T790(E)(A13 KING GUIDELINE ' INDUSTRIAL ELECTRONICS N3 7.3 | f H ee eee | a UNEAR ._ ] ry SLOPE | AMPLITUDE an | (PHYSICAL 4 J LENGTH) | | res SF 4oj---—-#---—-*-—- J { J | FALL | p++ le Time P4 SWEEP TIME | | (ELECTRICAL LENGTH) | | | ts PAT + oat To A mn OA” T2 Sketch — 1 mark; labels — 2marks (3) 74 e Dual-trace oscilloscopes have two vertical inputs that may produce two traces for the comparison of two different signals. ¢ Dual-beam oscilloscopes use two electronic guns that produce two individual electronic beams. (2 x 2) (4) ) fg) TOTAL: 100 Downloaded from hlayiso.com . ) Copyright reserved