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Past Questions — 2026
The speed of AC motor depends on:
A)
Frequency
B)
Number of poles
C)
Both (a) & (b)
D)
none of them
The speed of an AC motor, especially an induction or synchronous motor, depends on the supply frequency and the number of poles. The synchronous speed is given by Ns = 120f / P, where f is frequency and P is number of poles. Hence, both frequency and number of poles affect the motor speed. Option (a) alone is incomplete, option (b) alone is also incomplete, and (d) is incorrect.
In house wiring employing looping in and looping out system, phase Wire is looped in and looped out from:
A)
Socket
B)
ceiling rose
C)
lamp holder
D)
switch
In looping-in and looping-out wiring, the phase (live) wire is taken to the switch first and then looped onward to other points. The switch is therefore the point from which the phase wire is looped in and looped out. A ceiling rose or lamp holder is connected after the switch, while the socket is not the usual looping point for the phase wire in this context.
Megger is used to measure:
A)
Breakdown voltage of insulation
B)
insulation resistance
C)
earth resistance
D)
none of above
A megger (megohmmeter) is used to measure the insulation resistance of electrical cables, motors, and wiring. It applies a high DC test voltage and indicates resistance in megaohms. It is not primarily used to measure breakdown voltage, and earth resistance is measured by an earth tester, not a megger.
Efficiency of a power transformer is of the order of:
A)
75%
B)
50%
C)
98%
D)
100%
A power transformer is designed for very high efficiency, typically around 98% to 99% or even slightly higher at rated load, because its copper and core losses are very small compared with its power rating. 75% and 50% are far too low for a power transformer, while 100% is impossible in practice due to unavoidable losses.
Refrigeration and air -conditioning involve heat transfer using:
A)
water
B)
ice and water
C)
refrigerants
D)
none of above
Refrigeration and air-conditioning systems transfer heat by circulating a working fluid called a refrigerant. The refrigerant absorbs heat at low temperature and pressure and rejects it at higher temperature and pressure. Water or ice-water may be used in some cooling applications, but the basic heat-transfer medium in refrigeration and air-conditioning is the refrigerant.
Iron core of power transformer is laminated:
A)
to reduce copper losses
B)
to reduce hysteresis losses
C)
to reduce eddy current losses
D)
due to (b) and (c)
The iron core of a power transformer is laminated to break up the path of circulating currents induced in the core by alternating magnetic flux. These circulating currents are called eddy currents, and lamination increases the resistance to their flow, thereby reducing eddy current loss. Copper loss occurs in the windings, not in the iron core, so (a) is incorrect. Hysteresis loss depends on the magnetic properties of the core material, not on lamination, so (b) is incorrect. Since only eddy current loss is reduced by lamination, (d) is also incorrect.
Which is better earth resistance:
A)
1 ohm
B)
50 ohm
C)
100 ohm
D)
0.5 ohm
Lower earth resistance is better because it allows fault current to flow safely to ground and improves protection. Among the given values, 0.5 ohm is the lowest, so it is the best earth resistance. 1 ohm is also good, but higher than 0.5 ohm. 50 ohm and 100 ohm are too high for effective earthing.
If voltage supply to the energy meter is more than the rated value, energy meter will run:
A)
Slow
B)
fast
C)
neither slow or fast
D)
none of above
In an induction-type energy meter, if the applied voltage is higher than the rated value, the driving torque increases, so the meter tends to record more revolutions than actual consumption. Hence it runs fast. Option (a) slow is incorrect, and (c) is incorrect because over-voltage affects the meter reading.
The main function of power transformer is:
A)
to increase or decrease the d.c. voltage
B)
to increase or decrease the a.c. voltage
C)
to convert a.c. to d.c. vice-versa
D)
none of all
A transformer works on the principle of mutual induction and operates only with alternating current. Its main function is to step up or step down AC voltage in power systems. It cannot change DC voltage directly, and it does not convert AC to DC or vice versa. Therefore, option (b) is correct.
Suppliers fuse which is sealed is provided:
A)
before the energy meter
B)
after the main switch
C)
before distribution board
D)
after the energy meter
A supplier’s fuse (service fuse) is installed on the supply side, i.e., before the energy meter. It protects the incoming service line and the consumer’s installation from overcurrent. The energy meter should be protected by the supplier’s fuse, so it is not placed after the meter. Hence, option (a) is correct.
The electric motor helps the elevator car to:
A)
move downward
B)
move upward
C)
both (a) and (b)
D)
none of these
In an elevator, the electric motor drives the traction system so the car can move in both directions. It helps lift the car upward and, through controlled braking and counterweight action, also allows downward movement. Therefore, the correct answer is both upward and downward movement.
Two-way single pole switch controls:
A)
Connection of two wires to two positions
B)
connection of one wire to two positions
C)
connection of one wire to one position
D)
connection of two wire to four position
A two-way single pole switch is used to control one load from two different locations. It has two possible positions and connects the common terminal to one of two traveler wires. Hence, it controls the connection of two wires to two positions. Option (b) describes a one-way switch concept, while (c) and (d) do not correctly describe a two-way single pole switch.
Sparking occurs when a load is switched off because the circuit has:
A)
high inductance
B)
high impedance
C)
high resistance
D)
high Capacitance
When a load containing inductance is switched off, the current through the inductor cannot change abruptly. The collapsing magnetic field produces a large back EMF, which can cause sparking at the switch contacts. Hence sparking occurs due to high inductance. High resistance or high impedance would reduce current, and capacitance is not the main cause here.
Continuity of an electrical circuit is usually checked by:
A)
Ammeter
B)
voltmeter
C)
ohm meter
D)
all of above
Continuity of a circuit means checking whether the path is complete and has very low resistance. An ohmmeter is used to measure resistance, so it can verify continuity. An ammeter measures current, and a voltmeter measures voltage, so they are not the usual instruments for continuity testing. Therefore, the correct answer is ohm meter.
1(one) horse-power is equal to:
A)
546 W
B)
656 W
C)
746 W
D)
none of above
1 horse-power (HP) is a standard unit of power and is approximately equal to 746 watts. Therefore, option (c) is correct. Option (a) 546 W is incorrect because 546 W is not the standard conversion for 1 HP. Option (b) 656 W is also incorrect. Hence, the correct answer is 746 W.
Fans and lamps in domestic installation are connected in:
A)
series and parallel combination
B)
series
C)
parallel
D)
none of above
In domestic wiring, fans and lamps are connected in parallel so that each appliance gets the full supply voltage and can be operated independently. If one lamp or fan fails, the others keep working. In series connection, the voltage would be divided and all devices would be affected together, so that is not used for house wiring.
The number of power points allowed on 1(one) circuit in house wiring is:
A)
1 point of 500 watts
B)
2 points of 1000/2000 watts each
C)
3points of 500 watts each
D)
none of the above
In house wiring, a power circuit is generally restricted to a single power point with a load of about 500 W. This is to prevent overloading and to keep the wiring within safe current-carrying limits. Options (b) and (c) exceed the usual permissible load for one circuit, so they are incorrect. Hence, the correct answer is (a) 1 point of 500 watts.
The standard single phase AC supply voltage in India is:
A)
110V
B)
415V
C)
230V
D)
none of above
The standard single-phase AC supply voltage in India is 230 V. Option (b) 415 V is the standard three-phase line voltage, not single-phase. Option (a) 110 V is used in some countries, not India. Therefore, the correct answer is (c) 230V.
1(one) Ton of refrigeration is equal to:
A)
15,000 BTU/hr
B)
13,000 BTU/hr
C)
12,000 BTU/hr
D)
none of above
1 ton of refrigeration (1 TR) is defined as the rate of heat removal required to freeze 1 ton of water at 0°C into ice in 24 hours. Its standard equivalent is 3.517 kW, which is approximately 12,000 BTU per hour. Therefore, option (c) is correct. Options (a) and (b) are higher than the standard value, and (d) is incorrect.
If voltage supply to the energy meter is more than the rated value, energy meter will run:
A)
Slow
B)
fast
C)
neither slow or fast
D)
none of above
In an energy meter, if the applied voltage is higher than the rated voltage, the operating torque increases and the meter tends to over-register energy, so it runs fast. Option (a) is incorrect because slow running is generally associated with low voltage or other error conditions. Option (c) is incorrect because the meter is affected by voltage variation. Option (d) is incorrect because the correct effect is given in option (b).
As per I.E Rules Permissible leakage current in any electrical installation is:
A)
1/500 parts of the total current
B)
1/100 parts of the total current
C)
1/5000 parts of the total current
D)
none of the above.
As per the Indian Electricity Rules, the permissible leakage current in an electrical installation is limited to 1/500 of the total current. This is a safety provision to ensure that leakage remains very small and does not indicate faulty insulation or a dangerous condition. Hence, option (a) is correct. The other options give either too high or too low a leakage limit and do not match the rule.
If a piece of metal wire is stretched, its resistance will increase:
A)
True
B)
False
C)
Both (a) and (b) are true
D)
Both (a) and (b) are false
When a metal wire is stretched, its length increases and its cross-sectional area decreases. Since resistance is given by R = ρL/A, both changes cause the resistance to increase. Therefore, the statement is true. Option (b) is incorrect because stretching does not decrease resistance. Options (c) and (d) are incorrect because they combine contradictory statements.
The S.I. Unit of luminous flux is:
A)
Lux
B)
lumen
C)
candela
D)
none of above
Luminous flux is the total quantity of light energy emitted per second, and its SI unit is the lumen. Lux is the unit of illumination (luminous flux per unit area), and candela is the SI unit of luminous intensity. Therefore, the correct answer is lumen.
Type of lift that is used in offices is:
A)
passenger lift
B)
hospital lift
C)
car lift
D)
Goods lift
An office building primarily requires a lift meant for carrying people, so the correct type is a passenger lift. Hospital lifts are designed for stretchers and medical use, car lifts are for vehicles, and goods lifts are meant for transporting materials rather than office occupants.
A 100-W lamp gives a luminous flux of 3000 lm. Its efficiency is:
A)
30 lm/W
B)
300 lm/W
C)
3.33%
D)
30%
Efficiency in illumination problems is taken as luminous efficacy = luminous flux / power input. Here, efficacy = 3000 lm / 100 W = 30 lm/W. Option (b) is too high, and options (c) and (d) are percentages, not the required unit lm/W.