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ISRO TECHNICAL ASSISTANT MODEL PAPER (ELECTRONICS) SET-2
1. What is the color code for a 4-band 1Ω and 10% tolerance resistor?
A.Red, Red, Brown, Gold
B.Orange, silver, Black, Gold
C.Red, Red, Black, Gold
D.Brown, Black, Gold, Silver
Ans: 10x10-1 ± 10%
2. An 8-ohm resistor is in series with a lamp. The circuit current is 1 A.
With 20 V applied, what voltage is being allowed for the lamp?
A.4 V B.8 V C.12 V D.20 V
3. What is the reactive power in the given circuit?
A. 0 VAR
B. 691µ VAR
C. 44.23 mVAR
D. 1.45 kVAR
Ans: Reactive power is the amount power that is sent back to the source from load.
We know that,
p=V2/Z
Here Z is the reactance of capacitor which denoted by Xc
Xc=1/(2*pi*f*c)
Xc=1446.8631 ohm
P=V2/Xc
P=64/1446.8631
P=44.233 mw
4.With a square wave input, an RL differentiator circuit with an output across the inductor will produce
what type of waveform?
A. dc
B. short time-duration pulses
C. exponential-shaped pulses
D. only a phase shift
5. What is the band pass (F1 – F2) of an RLC filter that resonates at 150 kHz and has a coil Q of 30?
A. 100.0 kHz to 155.0 kHz
B. 147.5 kHz to 152.5 kHz
C. 295.5 kHz to 4500 kHz
D. 149,970 Hz to 150,030 Hz
Ans:B.w=fr/Q B.W=150K/30 =5KHz f1+f2=5KHz if f1=f2 the f1=f2=2.5KHz
F1 = fr-f1=150-2.5KHz=147.5KHz F2 = fr+f1=150+2.5KHz=152.5KHz
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ISRO TECHNICAL ASSISTANT MODEL PAPER (ELECTRONICS) SET-2
6. What is the current through the LED?
A. 0 mA
B. 23 mA
C. 18 mA
D. 13 mA
Ans: I = V/R
R = 330 , V = 6 - 1.5V (LED drop voltage) So V = 4.5V
I = 4.5/330 = 0.013 A or 13 mA
7. What value of input resistance is needed in the given circuit to produce the given output voltage&
Find Voltage Gain of the circuit?
A. 50K & 51
B.4 k & 50
C. 4.08 k & 0.005
D. 5 k & 20
Ans: |Vo |= |Vin (-Rf/R1)|
R1=(Rf/Vout )* Vin = (200K/3)*60x10-3 = 4K AV = Vo/Vin = 3/60x10-3 = 50
8. What are the effects of moving a closed wire loop through a magnetic field?
A. A voltage is induced in the wire.
B. A current is induced in the wire.
C. The polarity across the wire depends on the direction of motion.
D. All of the above
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ISRO TECHNICAL ASSISTANT MODEL PAPER (ELECTRONICS) SET-2
9. The depletion-mode MOSFET
A. can operate with only positive gate voltages
B. can operate with only negative gate voltages
C. cannot operate in the Ohmic region
D. can operate with positive as well as negative gate voltages
10. In the classic three-op-amp instrumentation amplifier, the differential voltage gain is usually
produced by the
A. first stage
B. second stage
C. mismatched resistors
D. output op-amp
11. What is the voltage across R1 if the P-N junction is made of silicon?
A. 12 V
B.11.7 V
C.11.3 V
D.0 V
Ans:Vr = 12-0.7 = 11.3V
12. The Q point on a load line may be used to determine:
A. VC
B.VCC
C.VB
D.IC
13. What is the transconductance of an FET when ΔID = 1 mA and ΔVGS = 1 V?
A. 1 kS
B. 1 mS
C. 1 kΩ
D. 1 mΩ
Ans: gm=ΔID/ΔVGS = 1mA/1 = 1mS
14. What is the difference between binary coding and binary coded decimal?
A. Binary coding is pure binary.
B. BCD is pure binary.
C. Binary coding has a decimal format.
D. BCD has no decimal format.
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ISRO TECHNICAL ASSISTANT MODEL PAPER (ELECTRONICS) SET-2
15. For the logic circuit shown in Fig.P1.19, the required input condition (A,B,C) to
make the output (X)=1 is
A. 1, 0, 1
B. 0, 0, 1
C. 1, 1, 1
D. 0, 1, 1
16. What is the principal advantage of using address multiplexing with DRAM memory?
A. reduced memory access time
B. reduced requirement for constant refreshing of the memory contents
C. reduced pin count and decrease in package size
D. no requirement for a chip-select input line, thereby reducing the pin count
17. A binary-weighted digital-to-analog converter has an input resistor of 100 kΩ . If the resistor is
connected to a 5 V source, the current through the resistor is:
A. 50µ A
B. 5 mA
C. 500µ A
D. 50 mA
Ans: I=V/R =5/100K ohms=0.05mA =50µ A
18. Calculate the temperature coefficient in %/° C of a 10-V nominal Zener diode at 25° C if the nominal
voltage is 10.2 V at 100° C.
A. 0.0238
B.0.0251
C. 0.0267
D. 0.0321
Ans: Tempcoeff=(change in voltage/change in temp)x voltage at inital temperature
Tcoeff=(10.2-10)/(100-25) x 10= 0.2/75 x10 =0.026666... = 0.0267
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ISRO TECHNICAL ASSISTANT MODEL PAPER (ELECTRONICS) SET-2
19. What is the voltage measured from the negative terminal of C4 to the negative terminal of the
transformer?
A. –10 V
B. –20 V
C.
10 V
D.
20 V
Ans: This circuit is called voltage quadrupler. 4 times the input voltage which is 20 but the capcitor
polarity is given in opposite direction, so -20V. If it has another capacitor brunch C5 then it would be
what 5 times of the transformer voltage.
20. In this circuit βDC = 100 and VIN = 8 V. The value of RB that will produce saturation is:
A. 92 kΩ
B. 9.1 MΩ
C. 100 kΩ
D. 150 kΩ
Ans: vbb=vbe+ib*rb
vbb=8; vbe=0.7
ib=ic/beta
beta=100
ic=vcc/rc
ib=(20/2500)/100
ib=0.08ma
rb=(vbb-vbe)/ib
(8-0.7)/0.08=91.25kohms
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ISRO TECHNICAL ASSISTANT MODEL PAPER (ELECTRONICS) SET-2
21. A phase-locked loop (PLL) is a feedback circuit consisting of a:
A. phase detector.
B. low-pass filter.
C. VCO.
D. all of the above
22. Refer to figure given below. Calculate the value of VDS.
A. 0 V
B. 2 V
C. 4 V
D. –2 V
Ans: Vdd-[Id(Rd+Rs)]= 20-[6mA(3K)]= 20-18 = 2v
23.Refer to this figure. Increasing the values of the filter section resistors in this circuit will
cause the fc to
A. increase.
B. decrease.
C. remain the same.
D. increase and then decrease.
Ans: Figure given is of second order LPF
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ISRO TECHNICAL ASSISTANT MODEL PAPER (ELECTRONICS) SET-2
24. Refer to the given figure. The resonant frequency is controlled by
A. C3 and L1.
B. C2, C4, C5, and L1.
C. C3, C4, C5, and L1.
D. C3, C4, C5, and L2.
Ans:Hartley oscillator In the above circuit R3 & C2 acts as a biasing elements, C3, C4, C5, L1 acts as a
resonant circuit.
25. The technique of assigning a memory address to each I/O device in the computer system is called:
A. memory-mapped I/O
B. ported I/O
C. dedicated I/O
D. wired I/O
26. Implementing the expression AB + CDE using NAND logic, we get:
A.
(A)
B.
(B)
C.
(C)
D.
(D)
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ISRO TECHNICAL ASSISTANT MODEL PAPER (ELECTRONICS) SET-2
27. Calculate the output voltage if V1 = V2 = 700 mV.
A. 0 V
B. –12 V
C. 12 V
D. –8 V
Ans: Consider the first stage op-amp.
G= -(500k/250k);
Vo1 (output of first stage op-amp)= -2 V1:
second stage op-amp has inputs as V2 and -(2*V1)
so Vo = - {[(-2*V1)*(500k/100k)]+(V2*(500k/50k))} (Summer)
Vo = - {-10V1+10V1}
Vo = 0V;
28. The voltage between the emitter and collector of a silicon transistor when the transistor is biased to
be at the edge of saturation is:
A.5 volts.
B.10 volts.
C.0.1 volts.
D.0.3 volts.
Ans:VEOS = 0.3V
29. Given a MOD-14 ripple counter using J-K flip-flops. If the clock frequency to the counter is 30 KHz,
then the output frequency of the counter will be
A. 2.2 KHz.
B. 30 KHz.
C. 2.14 KHz.
D. 3.2 KHz.
Ans: clock frequency gets divided by n (n = no of mod)fout=30KHz/14=2.14 KHz
30. If the output voltage of a bridge rectifier is 100V, the PIV of diode will be
A.100√2
B.200/
C.100
D./
Ans: Peak inverse voltage = max secondary voltage
=
=100
=
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