ELECTRICAL 131 IMPORTANT EXPECTED OBJECTIVE QUESTIONS AND ANSWER PDF FOR VIZAG MT EXAM 2017

Q.1.The “Superposition theorem” is essentially based on the
concept of

(A)  duality.
(B) linearity.

(C) reciprocity.
(D) non-linearity.

Ans: B

Q.2  Cells are connected in parallel in order to

(A)  increase the voltage available.

(B)  reduce cost of wiring.

(C)  increase the current available.
(D)  reduce the time required to fully charge them after use.

Ans: C

Q.3  The power factor of a purely resistive circuit is

(A) zero.
(B) unity.

(C) lagging.
(D) leading.

Ans: B

Q.4  The power taken by a 3-phase load is given by the expression

(A) 3 VL  IL cos f .
(B) 3 VL  IL cos f .

(C)  3 VL IL sin f .
(D) 3 VL  IL sin f .

Ans: B

Q.5 Which of the following generating stations has the minimum running cost?

(A)  hydro-electric station.
(B)  nuclear power station.

(C)  thermal power station.
(D)  diesel power plant.

Ans: A

Q.6 Which of the following motors has a high starting torque?

(A) ac series motor.
(B)  dc series motor.

(C) induction motor.
(D)  synchronous motor.

(A) voltage.
(C) power.

Ans: A

Q.8 The effect of increasing the length of the air gap in an induction motor will be to increase

(A)  power factor.
(B) speed.

(C) magnetising current.
(D)  air-gap flux.

Ans: C

Q.9  The combined resistance of two equal resistors connected in parallel is equal to

(A)   One half the resistance of one resistor.

(B)   Twice the resistance of one resistor.

(C)   Four times the resistance of one resistor.

(D)   One fourth the resistance of one resistor.

Ans: A

Q.10 Superposition theorem can be applicable only to circuits having elements.

(A) Non- linear
(B) Passive

(C) Resistive

(D)  Linear bilateral

Ans: D

Q.11   The Q- factor of a coil is given by

(A) Its power factor cos j.

(B) Ratio of max. energy stored & energy dissipated per cycle..

(C) Reciprocal of its power factor.

(D) Ratio R/Z.

Ans: C

Q.12 Voltage equation of a dc motor is

(A) V = Eb + Ia Ra.
(B) Eb = V + Ia Ra.

(C)  V = Eb  / Ia Ra.

(D) V = Eb  + Ia 2Ra.

Ans: A

Q.13  The efficiency of a transformer is maximum when

(A)  It runs at half full load.
(B)  It runs at full load.

(C)  Its Cu loss equals iron loss.
(D)  It runs overload.

Ans: C

Q.14  The crawling in an induction motor is caused by

(A) Improper design of the machine

(B) Low voltage supply.

(C) High loads.
(D)  Harmonics developed in the motor.

Ans: D

Q.15  The starting winding of a single-phase motor is placed in

(A)  Rotor.
(B) Stator.

(C) Armature.
(D) Field.

Ans: B

Q.16 Reduction in the capacitance of a capacitor- start motor results in reduced

(A) Noise.
(B) Speed.

(C) Starting torque.
(D) Armature reaction.

Ans: C

Q.17 In an ac circuit, the ratio of kW / kVA represents

Q.19 Thevenin’s equivalent circuit consists of

(A) Series combination of RTh, ETh and RL.

(B) Series combination of RTh, ETh.

(C) Parallel combination of RTh, ETh.

(D) Parallel combination of RTh, ETh and RL.

Ans: B

Q.20  In an R – L –C  circuit,  the phase of the  current  with respect  to the circuit  voltage will  be.

(A)  Leading.
(B) Same.

(C) Lagging.
(D)  Depends upon the value of Land C.

Ans: D

Q.21 The frequency of DC supply is
(A)  Zero.
(B)  16 ½ Hz
(C) 50 Hz.
(D)  100 Hz

Ans: A

Q.22 Load factor is defined as the ratio of
(A) Average Demand / Max. Demand.
(B) Max. Demand / Average Demand.
(C) Average Demand / Connected load.
(D) Connected load / Max. Demand.

Ans: A

Q.23 Static Capacitors are used for.

(A) Power improvement.
(B)  Current improvement.

(C) Voltage improvement.
(D)  Power factor improvement.

Ans: D

Q.24 The speed of an induction motor.

(A) Decreases too much with the increase of load.

(B) Increases with the increase of load.

(C) Decreases slightly with the increase of load.

(D) Remains constant with the increase of load.

Ans: C

Q.25 Centrifugal switch is provided for disconnecting the auxiliary winding in a

(A)  Capacitor- start motor.
(B)  Capacitor run motor.

(C) Reluctance motor.
(D)  Hysteresis motor.

Ans: A

Q.26 Rotating magnetic field is produced in a _.

(A) Single- phase induction motor.

(B) Three- phase induction motor.

(C) DC series motor.
(D) AC series motor.

Ans: B

Q.27 The frequency of the secondary voltage of a transformer will be.

(A) Less than the frequency of the primary voltage.

(B)   Equal to the primary voltage.

(C) Greater than the frequency of the primary voltage.

(D) Very much greater than the frequency of the primary voltage.

Ans: B

Q.28  The demand factor for the electrical system is the ratio of

(A) Maximum demand to connected load

(B) Maximum demand to average load

(C) Average power to maximum power

(D) Relative power to total power

Ans: A

Q.29  When a low resistance is connected in parallel with a high resistance, the combined resistance is

(A) Always more than the high resistance.

(B) Always less than the low resistance.

(C)  Always between the high resistance & low resistance.

(D)  Either lower or higher than low resistance depending on the value of high resistance.

Ans: B

Q.30 Q factor of an inductive coil is given by

(A) R/Z

(B)  2 n f r/R

(C)   2 n f L/R

(D) A r/A

Ans: B

Q.32 If the readings of the two wattmeter’s in the 2-wattmeter method of power measurement are 4.5 kW and 3.5 kW respectively and the latter reading has been obtained after reversing the current coil of the wattmeter. What will be the total power in kW?

(A) 1
(B) 3.5

(C) 4.5
(D) 8

Ans: A

Q.33 A DC series motor is best suited for driving

(A)  Lathes.
(B)  Cranes and hoists.

(C)  Shears and punches.

(D)  Machine tools.

Ans: B

Q.34 Transformer cores are built up from laminations rather than from solid metal so that

(A) Oil penetrates the core more easily.

(B) Eddy current loss is reduced.

(C) Less lamination is required for the windings.

(D) Turn ratio is higher than voltage ratio.

Ans: B

Q.35 In a DC series motor increase in load current results in

(A) Decrease in speed
(B)  Increase in speed

(C) Better commutation

(D) Increase in the back emf.

Ans: A

Q.36 The starting torque of a 1-phase induction motor is

(A) High.
(B) Moderate.

(C) Low.
(D) Zero.

Ans: D

Q.37 An electric motor in which rotor and stator fields rotate simultaneously is called a motor.

(A) DC
(B) Induction

(C) Synchronous
(D) Universal

Ans: C

Q.38 In India, electrical power is transmitted by

(A)  1 – phase a.c. system.
(B) 3-wire d.c. system.

(C)  3-phase 3-wire a.c. system.

(D) 2-wire d.c. system.

Ans: C

Q.39 In ac circuit the product of voltage and current is known as

(A) Power.
(B) Real power.

(C) Resistive power.
(D) Apparent power.

Ans: D

Q.40 A network that does not have either voltage or current sources is called

(A)  Active network.
(B) Passive network.

(C) Resistive network.
(D) Dummy network.

Ans: B

Q.41 The Power- factor at resonance in R-L-C circuit is

(A) Zero.
(B) Unity.

(C) 0.5 lagging.
(D) 0.5 leading.

Ans: B

Q.42   In an 8 – pole wave connected motor armature, the number of parallel paths are

(A) 8
(B) 4

(C) 2
(D) 1

Ans: C

Q.43 Transformer core is laminated to

(A) Reduce the copper losses.

(B) Reduce the core losses.

(C) Reduce the eddy current losses.

(D) None of these.

Ans: C

Q.45   Star – delta starter of an induction motor

(A) Inserts resistance in rotor circuit.

(B) Inserts resistance in stator circuit.

(C) Applies reduced voltage to rotor.

(D) Applies reduced voltage to stator.

Ans: D

Q.46 Stator core of an induction motor is made of

Ans: A

Q.49 Which DC motors has approximately constant speed?

(A) Series motor.
(B)  Shunt motor

(C) Cumulatively compound motor

(D) All of the  above.

Ans: B

Q.50 Which of the following bulbs will have the least resistance?

(A) 220V, 60W
(B)  220 V, 100 W

(C)  115 V, 60 W
(D)  115V, 100 W

Ans: D

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) lash

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.62Which of the following power plant has the maximum efficiency?

(A)  Thermal
(B) Hydroelectric

(C) Nuclear
(D) Diesel

Ans:C

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 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 mV .

Ans: A

Q.49 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.50  A voltage source having an open-circuit voltage of 100 V and internal resistance of 50 W is equivalent to a current source

(A) 2A in parallel with 50 W .
(B) 2A with 50 W in series.

(C) 0.5A in parallel with 50 W .
(D) 2A in parallel with 100 W .

Ans: A

Q.51 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.52 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.53  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.54  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.55   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.56 Ideal operational amplifier has input impedance of

(A)  1MW .
(B) infinity.

(C) zero.
(D)  1W .

Ans: B

Q.57 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.58 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.59 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.9 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, Georg 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.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

Q.101 The foundation on which an IC is built is called
(A) an insulator.
(C) a wafer.
(B)  a base.
(D) a plate.