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Past Questions
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.
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.
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.
If 2(two) lamps of 100watt each are connected in series:
A)
each lamp will glow very bright
B)
first lamp will glow brighter than second lamp
C)
each lamp will glow less brightly than single lamp connected to the same voltage source
D)
all of the above
When two identical 100 W lamps are connected in series, the supply voltage is divided between them, so each lamp gets less than its rated voltage. Since brightness depends on power consumed, each lamp will glow dimmer than a single lamp connected directly across the same voltage source. Option (a) is wrong because brightness does not increase in series. Option (b) is wrong because the lamps are identical, so both get the same current and glow equally. Therefore, (c) is correct.
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 only on alternating current (AC) because it operates on the principle of mutual induction. Its main function is to step up or step down AC voltage. It cannot directly change DC voltage, and it does not convert AC to DC or vice-versa. Therefore, option (b) is correct.
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.
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.
In a.c. circuit, fuse is inserted only in:
A)
Earth wire
B)
neutral wire
C)
live wire
D)
none of above
In an a.c. circuit, the fuse is connected in the live wire so that when excessive current flows, it breaks the supply to the appliance completely. If it were placed in the neutral wire, the appliance could still remain connected to the live potential, which is unsafe. Hence, the correct answer is live wire.
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.
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.
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.
In two W meter method, if the power factor is unity, then:
A)
W1 > W2
B)
W1 < W2
C)
W1 = W2
D)
none of above
In the two-wattmeter method, the power factor angle is given by tan φ = √3 (W1 − W2) / (W1 + W2). If the power factor is unity, then φ = 0°, so tan φ = 0. This means W1 − W2 = 0, hence W1 = W2. Therefore, both wattmeters read the same value. Options (a) and (b) are incorrect because there is no difference between the readings at unity power factor.
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.
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).
In electrical instruments, electrical energy is converted to:
A)
Light energy
B)
mechanical energy
C)
chemical energy
D)
heat energy
In electrical measuring instruments, the electrical quantity being measured produces a deflecting effect that is converted into mechanical motion of the pointer. Hence, electrical energy is converted into mechanical energy. The other options are not correct because light, chemical, and heat energy are not the usual final output in indicating electrical instruments.
Electrical energy is measure in:
A)
Ohm meter
B)
volt meter
C)
amperemeter
D)
energy meter
Electrical energy is measured using an energy meter (also called a kilowatt-hour meter). An ohm meter measures resistance, a volt meter measures voltage, and an ammeter measures current. Hence, the correct choice is energy meter.
A generator is a machine which converts:
A)
electrical energy into mechanical energy
B)
mechanical energy into electrical energy
C)
both (a) and (b)
D)
none of the above
A generator works on the principle of electromagnetic induction and converts mechanical energy supplied by a prime mover into electrical energy. Option (a) is the reverse process and describes a motor. Option (c) is incorrect because a single generator does not convert both ways in normal operation.
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.
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.
A ‘short circuit’ is that which:
A)
Uses short pieces of wire
B)
goes only a short distance
C)
is used for dimming light
D)
offer very low resistance path for current to flow
A short circuit occurs when current finds an unintended path with very low resistance, causing a large current to flow. Option (a) is incorrect because it refers to wire length, not electrical behavior. Option (b) is unrelated to the definition. Option (c) is also incorrect because dimming light is not the meaning of short circuit; in fact, a short circuit is usually dangerous and can damage circuits.
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 both (b) and (c)
The iron core of a power transformer is laminated to increase the resistance to circulating currents induced in the core. This breaks the core into thin insulated sheets, thereby reducing eddy current losses. Copper losses occur in the windings, not in the core. Hysteresis loss is reduced by using suitable core material, not by lamination. Hence, the correct answer is (c).
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.
Switch is always placed in:
A)
Neutral wire
B)
live wire
C)
any of the two
D)
earth wire
In house wiring, the switch is always connected in the live wire so that when it is OFF, the appliance is disconnected from the supply voltage. If the switch were placed in the neutral wire, the appliance could still remain live and unsafe. The earth wire is only for safety grounding, not for switching, and 'any of the two' is incorrect in standard wiring practice.