Choose correct or the best alternative in the following:
Q.51 Resistance of a wire is r ohms. The wire is stretched to double its length, then its resistance
in ohms is
(A) r/2 (B) 4r
(C) 2r (D) r/4
Ans: B
Q.52 An electric machine will have high efficiency when
(A) input/output ratio is low (B) reactive power is more
(C) kWh consumption is low (D) losses are low
Ans: D
Q.53 Which type of loss is not common to transformers and rotating machines?
(A) Eddy current loss (B) Copper loss
(C) Hysteresis loss (D) Windage loss
Ans: D
Q.54 The difference between the synchronous speed and the actual speed of an induction motor is
known as
(A) Regulation (B) back lash
(C) slip (D) lag
Ans: C
Q.55 In two wattmeter method of power measurement, if one of the wattmeter shows zero
reading, then it can be concluded that
(A) Power factor is unity (B) Power factor is zero
(C) Power factor is 0.5 lagging (D) Power factor is 0.5 leading
Ans: C
Q.56 Which of the following will remain the same in all parts of a series circuit?
(A) Voltage (B) Current
(C) Power (D) Resistance
Ans: B
Q.57 Which single phase motor would you select for a tape recorder?
(A) Reluctance motor (B) Hysteresis motor
(C) Synchronous motor (D) Universal motor
Ans: B
Q.58 Under the condition of resonance, RLC series circuit behaves as a,
(A) Purely resistive circuit. (B) Purely inductive circuit.
(C) Capacitive circuit. (D) Reactive circuit.
Ans:A
Q.59 During charging, the electrolyte of a lead acid cell becomes
(A) Stronger. (B) Weaker.
(C) Water. (D) Diluted.
Ans:D
Q.60 As compared to shunt and compound motors, series motor have the highest torque because of
its comparatively __________ at the start.
(A) Lower armature resistance. (B) Stronger series field.
(C) Fewer series turns. (D) Larger armature current.
Ans:D
Q.61 The input of an ac circuit having p.f. of 0.8 lagging is 20 kVA. The power drawn by the
circuit is __________ kW.
(A) 12. (B) 20.
(C) 16. (D) 8.
Ans: C
Q.62 The voltage ratio of the transformer is given as
(A) ES EP (B) TS TP
(C) TP TS (D) EP TS
Ans:A
Q.63 The relationship between the frequency of ac wave and the time period is given by
(A) f = T (B) f = 1 T2
(C) f = 1 T (D) 2 f = T
Ans: C
Q.64 Which of the following power plant has the maximum efficiency?
(A) Thermal (B) Hydroelectric
(C) Nuclear (D) Diesel
Ans:C
Q.65 Three capacitors of value 8μF , 16μF and 32μF are connected in series, the total
capacitance will be
(A) 32 7 μF . (B) 7.32 μF .
(C) 56 μF . (D) 32 μF .
Ans: A
Q.66 The following components are all active components
(A) a resistor and an inductor.
(B) a diode, a BJT and an FET.
(C) a capacitor, and an inductor.
(D) an Opamp, a BJT and thermionic triode.
Ans: B
Q.67 In forward mode NPN BJT, if we increase the voltage VCC , the collector current increases
(A) due to ohm’s law, higher VCC causes higher current.
(B) due to base width decrease less carrier recombine in the base region.
(C) as the gradient of the minority carriers in the base region becomes steeper.
(D) due to both the reasons (B) and (C).
Ans: D
Q.68 The barrier voltage ( ) Vr or Vo in a junction diode is the effect of
(A) the p-side and n-side of the junction forming a battery.
(B) the emf required to move the holes fast enough to have the mobility equal to that of
the electrons.
(C) the recombination of charge carriers across the junction leaving behind the opposite
charged ions.
(D) the voltage needed to make the semiconductor material behave as a conductor.
Ans:C
Q.69 An emitter follower has high input impedance because
(A) large emitter resistance is used.
(B) large biasing resistance is used.
(C) there is negative feedback in the base emitter circuit.
(D) the emitter-base junction is highly reverse biased.
Ans: C
Q.70 In a differential amplifier an ideal CMRR is
(A) infinity. (B) zero.
(C) –1. (D) +1.
Ans: A
Q.71 FET is advantageous in comparison with BJT because of
(A) high input impedance. (B) high gain-bandwidth product.
(C) its current controlled behaviour. (D) high noise immunity.
Ans: A
Q.72 The emission of electrons in a vacuum diode is achieved by
(A) electrostatic field. (B) magnetic field.
(C) heating. (D) electron bombardment.
Ans: C
Q.73 The colour code of a resistor of nominal value 2.7KW± 10% is
(A) Red, violet, red and silver. (B) Red, violet, yellow and gold.
(C) Red, violet, orange and silver. (D) Red, violet, red and gold.
Ans: A
Q.74 Capacitor that can have the highest capacitance value is
(A) Mica (B) Paper
(C) Electrolytic (D) Ceramic
Ans: C
Q.75 The equivalent current-source representation for a voltage-source with open circuit voltage 12
V and internal resistance 3 ohms is
(A) a current-source of strength 4A in shunt with a resistance of 6W.
(B) a current –source of strength 4A in series with a resistance of 3W.
(C) a current-source of strength 4A in shunt with a resistance of 3 ohms.
(D) a current-source of strength 4A in shunt with a resistance of 36 ohms.
Ans: C
Q.76 An intrinsic semiconductor at absolute zero temperature
(A) has a large number of holes.
(B) behaves like an insulator.
(C) behaves like a metallic conductor.
(D) has few holes and same number of electrons.
Ans: A
Q.77 The current flow through a Ge PN junction diode with a forward bias of 0.22 Volt and a
reverse saturation current of 1 mA at 25 C
o
is around
(A) 6.3 A (B) 5.22 A
(C) 4 mA (D) 5.1 mA
Ans: B
Q.78 For the operation of a depletion-type N-MOSFET, the gate voltage has to be
(A) low positive (B) high positive
(C) high negative (D) zero
Ans: D
Q.79 The typical operating voltage for LED’s ranges from
(A) 0.2 V to 0.6 V. (B) 6 V to 10 V.
(C) 1.5 V to 2.5 V. (D) 9 V to 10 V.
Ans: C
Q.80 Capacitors for integrated circuits
(A) cannot be made using diffusion techniques.
(B) can be made with very high values of capacitance.
(C) are always discrete components connected externally.
(D) can be made using silicon dioxide as the dielectric.
Ans: D
Q.81 The magnitude of variation in the output voltage for a 10 V regulated dc power supply of
0.002% regulation will be
(A) 0.2 mV. (B) 0.002 mV.
(C) 0.02 mV. (D) 0.2 μV .
Ans: A
Q.82 For the circuit shown in Fig.1, the output voltage is given by
(A) ( 2 1)
1
F
o v v
R
R
v = − .
(B) ( ) 2 1 2
1
F
o v v v
R
R
v = − − .
(C) ( ) 2 1 2
1
F
o v v v
R
R
v = − + .
(D) ( )
( ) 1 F
2 1
o R R
v v
v +
= − .
Ans: C
Q.83 Which one of the following statements is not true?
(A) Capacitance is a measure of a capacitor’s capability to store charge.
(B) A capacitor offers high impedance to ac but very low impedance to dc.
(C) A capacitor is also used as bypass capacitor.
(D) Capacitors are used to couple alternating voltages from one circuit to another and
at the same time to block dc voltage from reaching the next circuit.
Ans: B
Q.84 A voltage source having an open-circuit voltage of 100 V and internal resistance of 50W is
equivalent to a current source
(A) 2A in parallel with 50W. (B) 2A with 50W in series.
(C) 0.5A in parallel with 50W. (D) 2A in parallel with 100W.
Ans: A
Q.85 In a Zener diode large reverse current is due to
(A) collision. (B) presence of impurities.
(C) rupture of bonds (D) lower resistance in reverse biased
region.
Ans: D
Q.86 Ripple factor of a full-wave rectifier without filter will be
(A) 0.2. (B) 0.48.
(C) 0.24. (D) 1.21.
Ans: B
Q.87 JFET has main drawback of
(A) having low input impedance.
(B) having high output impedance.
(C) being noisy.
(D) Having small gain-bandwidth product.
Ans: D
Q.88 A UJT has
(A) stable negative resistance characteristics.
(B) low firing current.
(C) use as a waveform generator.
(D) all of these characteristics.
Ans: D
Q.89 For thermionic emission
(A) a material with high work function is preferable.
(B) a material with low work function is preferable.
(C) the work function of the material has no importance.
(D) None of these is true.
Ans: B
Q.90 Ideal operational amplifier has input impedance of
(A) 1MW . (B) infinity.
(C) zero. (D) 1W .
Ans: B
Q.91 The CE configuration amplifier circuits are preferred over CB configuration amplifier circuits
because they have
(A) lower amplification factor.
(B) Larger amplification factor.
(C) high input resistance and low output resistance.
(D) none of these.
Ans: B
Q.92 The most commonly used type of electron emission in electron tubes is
(A) Photo-electron emission. (B) Thermionic emission.
(C) Field emission. (D) Secondary emission.
Ans: A
Q.93 The colour band sequence of a resistor is grey, Blue, gold, and gold. The range in which its
value must lie so as to satisfy the tolerance specified is between
(A) 7.5W and 8.5W (B) 3.12KW and 5.22KW
(C) 10.3KW and 12.31KW (D) 8.17W and 9.03W
Ans: D
Q.94 A device whose characteristics are very close to that of an ideal current source is
(A) a gas diode. (B) a BJT in CB mode.
(C) a BJT in CE mode. (D) a triode.
Ans: C
Q.95 In an N-type semiconductor, the concentration of minority carriers mainly depends upon
(A) the doping technique. (B) the number of donor atoms.
(C) the temperature of the material (D) the quality of the intrinsic material,
Ge or Si.
Ans: B
Q.96 When forward bias is applied to a junction diode, it
(A) increases the potential barrier.
(B) decreases the potential barrier.
(C) reduces the majority-carrier current to zero.
(D) reduces the minority-carrier current to zero.
Ans: B
Q.97 The theoretical maximum efficiency of a Bridge rectifier circuit is
(A) 48.2%. (B) 81.2%.
(C) 82%. (D) 40.6%.
Ans: B
Q.98 The input resistance of a common-collector configuration will be of the order of
(A) ~ 90KW (B) ~ 60KW
(C) ~ 150KW (D) 300KW and above
Ans: D
Q.99 A switching voltage regulator can be of the following type:
(A) step-down (B) step-up
(C) inverting (D) none of these
Ans: A
Q.100 A UJT contains
(A) four pn junctions (B) three pn junctions
(C) two pn junctions (D) one pn junction
Ans: D
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