Explore topic-wise MCQs in Testing Subject.

This section includes 657 Mcqs, each offering curated multiple-choice questions to sharpen your Testing Subject knowledge and support exam preparation. Choose a topic below to get started.

1.

In order that current should flow without causing excessive heating or voltage drop, the relay contacts should

A. have low contact resistance
B. be clean and smooth
C. be of sufficient size and proper shape
D. have all above properties
Answer» E.
Discussion
2.

The relay operating speed depends upon

A. the spring tension
B. the rate of flux built up
C. armature core air gap
D. all of the above
Answer» E.
Discussion
3.

D.C. shunt relays are made of

A. few turns of thin wire
B. few turns of thick wire
C. many turns of thin wire
D. many turns of thick wire
Answer» D. many turns of thick wire
Discussion
4.

Magnetic circuit breaker has ______ trip action.

A. delayed
B. instantaneous
C. both of the above
D. none of the above
Answer» C. both of the above
Discussion
5.

Thermal overload relays are used to protect the motor against over current due to

A. short-circuits
B. heavy loads
C. grounds
D. all of the above
Answer» C. grounds
Discussion
6.

Overload relays are of…… type

A. induction
B. solid state
C. thermal
D. all above
Answer» E.
Discussion
7.

Relays can be designed to respond to changes in

A. resistance, reactance or impedance
B. voltage and current
C. light intensity
D. all above
Answer» E.
Discussion
8.

Thermal circuit breaker has

A. delayed trip action
B. instantaneous trip action
C. both of the above
D. none of the above
Answer» B. instantaneous trip action
Discussion
9.

Arc in a circuit behaves as

A. a capackive reactance
B. an inductive reactance
C. a resistance increasing with voltage rise across the arc
D. a resistance decreasing with voltage rise across the arc
Answer» E.
Discussion
10.

A thermal protection switch can protect against

A. short-circuit
B. temperature
C. overload
D. over voltage
Answer» D. over voltage
Discussion
11.

Fault diverters are basically

A. fuses
B. relays
C. fast switches
D. circuit breakers
Answer» D. circuit breakers
Discussion
12.

With which of the following, a circuit breaker must be equipped for remote operation ?

A. Inverse time trip
B. Time-delay trip
C. Shunt trip
D. None of the above
Answer» D. None of the above
Discussion
13.

Which of the following medium is employed for extinction of arc in air circuit breaker

A. Water
B. Oil
C. Air
D. SF6
Answer» D. SF6
Discussion
14.

The arcing contacts in a circuit breaker are made of

A. copper tungsten alloy
B. porcelain
C. electrolytic copper
D. aluminium alloy
Answer» B. porcelain
Discussion
15.

SF6 gas

A. is yellow in colour
B. is lighter than air
C. is nontoxic
D. has pungent small
Answer» D. has pungent small
Discussion
16.

On which of the following routine tests are conducted ?

A. Oil circuit breakers
B. Air blast circuit breakers
C. Minimum oil circuit breakers
D. All of the above
Answer» E.
Discussion
17.

The main function of a fuse is to

A. protect the line
B. open the circuit
C. protect the appliance
D. prevent excessive currents
Answer» E.
Discussion
18.

The circuit has resistors, capacitors and semi-conductor diodes. The circuit will be known as

A. non-linear circuit
B. linear circuit
C. bilateral circuit
D. none of the above
Answer» B. linear circuit
Discussion
19.

The circuit whose properties are same in either direction is known as

A. unilateral circuit
B. bilateral circuit
C. irreversible circuit
D. reversible circuit
Answer» C. irreversible circuit
Discussion
20.

If the energy is supplied from a source, whose resistance is 1 ohm, to a load of 100 ohms the source will be

A. a voltage source
B. a current source
C. both of above
D. none of the above
Answer» B. a current source
Discussion
21.

For maximum transfer of power, internal resistance of the source should be

A. equal to load resistance
B. less than the load resistance
C. greater than the load resistance
D. none of the above
Answer» B. less than the load resistance
Discussion
22.

If resistance across LM in Fig. 2.30 is 15 ohms, the value of R is

A. 10 Q
B. 20 Q
C. 30 Q
D. 40 Q
Answer» D. 40 Q
Discussion
23.

Efficiency of power transfer when maximum transfer of power c xerosis

A. 100%
B. 80%
C. 75%
D. 50%
Answer» E.
Discussion
24.

For high efficiency of transfer of power, internal resistance of the source should be

A. equal to the load resistance
B. less than the load resistance
C. more than the load resistance
D. none of the above
Answer» C. more than the load resistance
Discussion
25.

The resistance LM will be

A. 6.66 Q
B. 12 Q
C. 18Q
D. 20Q
Answer» B. 12 Q
Discussion
26.

Kirchhoff s voltage law applies to circuits with

A. nonlinear elements only
B. linear elements only
C. linear, non-linear, active and passive elements
D. linear, non-linear, active, passive, time varying as wells as time-in-variant elements
Answer» E.
Discussion
27.

Kirchhoff s law is not applicable to circuits with

A. lumped parameters
B. passive elements
C. distributed parameters
D. non-linear resistances
Answer» D. non-linear resistances
Discussion
28.

A capacitor is generally a

A. bilateral and active component
B. active, passive, linear and nonlinear component
C. linear and bilateral component
D. non-linear and active component
Answer» D. non-linear and active component
Discussion
29.

Which of the following is non-linear circuit parameter ?

A. Inductance
B. Condenser
C. Wire wound resistor
D. Transistor
Answer» B. Condenser
Discussion
30.

“In any linear bilateral network, if a source of e.m.f. E in any branch produces a current I in any other branch, then same e.m.f. acting in the second branch would produce the same current / in the first branch”. The above statement is associated with

A. compensation theorem
B. superposition theorem
C. reciprocity theorem
D. none of the above
Answer» D. none of the above
Discussion
31.

"Maximum power output is obtained from a network when the load resistance is equal to the output resistance of the network as seen from the terminals of the load”. The above statement is associated with

A. Millman’s theorem
B. Thevenin’s theorem
C. Superposition theorem
D. Maximum power transfer theorem
Answer» E.
Discussion
32.

To determine the polarity of the voltage drop across a resistor, it is necessary to know

A. value of current through the resistor
B. direction of current through the resistor
C. value of resistor
D. e.m.fs. in the circuit
Answer» C. value of resistor
Discussion
33.

For a voltage source

A. terminal voltage is always lower than source e.m.f.
B. terminal voltage cannot be higher than source e.m.f.
Answer» C.
Discussion
34.

An ideal voltage source should have

A. large value of e.m.f.
B. small value of e.m.f.
C. zero source resistance
D. infinite source resistance
Answer» D. infinite source resistance
Discussion
35.

Thevenin resistance Rth is found

A. by removing voltage sources along with their internal resistances
B. by short-circuiting the given two terminals
C. between any two ‘open’ terminals
D. between same open terminals as for Etk
Answer» E.
Discussion
36.

The concept on which Superposition theorem is based is

A. reciprocity
B. duality
C. non-linearity
D. linearity
Answer» E.
Discussion
37.

Superposition theorem can be applied only to circuits having

A. resistive elements
B. passive elements
C. non-linear elements
D. linear bilateral elements
Answer» E.
Discussion
38.

Kirchhoffs voltage law is related to

A. junction currents
B. battery e.m.fs.
C. IR drops
D. both (b) and (c)
Answer» E.
Discussion
39.

Kirchhoffs current law is applicable to only

A. junction in a network
B. closed loops in a network
C. electric circuits
D. electronic circuits
Answer» B. closed loops in a network
Discussion
40.

According to Kirchhoffs voltage law, the algebraic sum of all IR drops and e.m.fs. in any closed loop of a network is always

A. negative
B. positive
C. determined by battery e.m.fs.
D. zero
Answer» E.
Discussion
41.

Kirchhoff s current law states that

A. net current flow at the junction is positive
B. Hebraic sum of the currents meeting at the junction is zero
C. no current can leave the junction without some current entering it.
D. total sum of currents meeting at the junction is zero
Answer» C. no current can leave the junction without some current entering it.
Discussion
42.

The most widely used rectifier is ……………….

A. half-wave rectifier
B. centre-tap full-wave rectifier
C. bridge full-wave rectifier
D. none of the above
Answer» D. none of the above
Discussion
43.

The maximum efficiency of a half-wave rectifier is ……………….

A. 40.6 %
B. 81.2 %
C. 50 %
D. 25 %
Answer» B. 81.2 %
Discussion
44.

A half-wave rectifier has an input voltage of 240 V r.m.s. If the step-down transformer has a turns ratio of 8:1, what is the peak load voltage? Ignore diode drop.

A. 27.5 V
B. 86.5 V
C. 30 V
D. 42.5 V
Answer» E.
Discussion
45.

The ……………….. filter circuit results in the best voltage regulation

A. choke input
B. capacitor input
C. resistance input
D. none of the above
Answer» B. capacitor input
Discussion
46.

A 1,000 V power supply would use ……….. as a filter capacitor

A. paper capacitor
B. air capacitor
C. mica capacitor
D. electrolytic capacitor
Answer» B. air capacitor
Discussion
47.

A 10 V power supply would use …………………. as filter capacitor.

A. paper capacitor
B. mica capacitor
C. electrolytic capacitor
D. air capacitor
Answer» D. air capacitor
Discussion
48.

If the PIV rating of a diode is exceeded, ………………

A. the diode conducts poorly
B. the diode is destroyed
C. the diode behaves like a zener diode
D. none of the above
Answer» C. the diode behaves like a zener diode
Discussion
49.

For the same secondary voltage, the output voltage from a centre-tap rectifier is ………… than that of bridge rectifier

A. twice
B. thrice
C. four time
D. one-half
Answer» E.
Discussion
50.

The PIV rating of each diode in a bridge rectifier is ……………… that of the equivalent centre-tap rectifier

A. one-half
B. the same as
C. twice
D. four times
Answer» B. the same as
Discussion