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Multiple choice question for engineering

Set 1

1. Power is ___________
a) rate of doing work
b) rate of producing voltage
c) rate of generating current
d) rate of overcoming friction

View Answer

Answer: a [Reason:] Power is defined as the rate of doing work. The unit of power is watt. In D.C. circuits, power is the product of the voltage consumed and the current flowing through a circuit. P = VI watts.

2. In A.C. circuits, power consumed is ________
a) product of voltage and current
b) it depends on the p.f. of the circuit in addition to voltage and current
c) it depends on the supply voltage
d) it depends on the magnitude of the circuit current

View Answer

Answer: b [Reason:] In a A.C. circuit, the power consumption is given by the expression, P=VI cos∅ where, V is the voltage across the circuit I is the current flowing through the circuit cos∅ is the power factor of the circuit.

3. In D.C. circuits, power is measured using ________
a) ohmmeter and galvanometer
b) ohmmeter and voltmeter
c) ammeter and voltmeter
d) ammeter and galvanometer

View Answer

Answer: c [Reason:] An ammeter is used to measure current flowing through a circuit, while a voltmeter is used to measure the voltage across the circuit. Hence in D.C. circuits, ammeter and voltmeter are used to measure power.

4. In A.C. circuits, power is measured using
a) voltmeter
b) ammeter
c) ohmmeter
d) wattmeter

View Answer

Answer: d [Reason:] A.C. circuits make use of power factor of the circuit in addition to the current flowing through the circuit and the voltage across the circuit. As a result, a wattmeter is used to measure A.C. power.

5. A wattmeter consists of a current coil and a potential coil.
a) True
b) False

View Answer

Answer: a [Reason:] Power in single phase A.C. circuits are measured by making use of a wattmeter. It consists of a current coil (cc) and a potential coil (pc). Current coil is connected with the load while the potential coil is connected across the supply.

6. A dynamometer type wattmeter consists of ________
a) only potential coil
b) potential and current coils
c) only current coil
d) no coils

View Answer

Answer: b [Reason:] Dynamometer type wattmeter is used for the measurement of A.C. as well as D.C. power. It consists of a fixed coil forming the current coil whereas the moving coil forms the potential coil.

7. Controlling torque is provided by gold springs.
a) True
b) False

View Answer

Answer: b [Reason:] In a Dynamometer type wattmeter, controlling torque is provided by two phosphor bronze hair springs. They act as leads to the current flowing through the coil. Also air friction damping is used.

8. In a Dynamometer type wattmeter, the fixed coil is split into ________
a) 4
b) 3
c) 2
d) 1

View Answer

Answer: c [Reason:] When a Dynamometer type wattmeter is used for the measurement of A.C. power, the fixed coil is split into two equal parts. The two parts are air-cored to avoid hysteresis loss.

9. When a current carrying coil is placed in the magnetic field.
a) no force is exerted
b) voltage is produced
c) power is generated
d) a force is exerted

View Answer

Answer: d [Reason:] When the current carrying coil of a Dynamometer type wattmeter is placed in the magnetic field of another current carrying coil, the moving coil experiences a force. As a result a deflection torque is generated and the moving coil undergoes deflection.

10. When the moving coil in a Dynamometer type wattmeter deflects
a) pointer moves
b) pointer doesn’t move
c) current flows
d) voltage is generated

View Answer

Answer: a [Reason:] In a Dynamometer type wattmeter, when the moving coil deflects the pointer moves over the scale. The pointer then comes back to rest at a point where the deflecting torque equals the controlling torque.

Set 2

1. Electronic multimeter measures ________
a) voltage, current and resistance
b) voltage and current
c) current and power
d) energy and power

View Answer

Answer: a [Reason:] A.C. as well as D.C. voltage, current and resistance can be measured by making use of an electronic multimeter. It is also known as an voltage-ohm meter.

2. Basic circuit of multimeter consists ________
a) of a.c. amplifier
b) of d.c. amplifier
c) operational amplifier
d) power amplifier

View Answer

Answer: b [Reason:] A.C. as well as D.C. voltage, current and resistance can be measured by making use of an electronic multimeter. The basic circuit of a multimeter is made up of d.c. amplifier circuit in the form of a balanced bridge.

3. Input signal magnitude is limited by ________
a) button
b) resistance
c) attenuator
d) voltage

View Answer

Answer: c [Reason:] A range switch is provided in an electronic multimeter in order to limit the input signal in terms of magnitude. We can adjust the input attenuator and limit the input signal in terms of magnitude.

4. Electronic multimeter consists of a rectifier.
a) True
b) False

View Answer

Answer: a [Reason:] An electronic multimeter is used for the measurement of A.C. as well as D.C. voltage, current and resistance. It consists of a rectifier section that is used to convert the a.c. input signal to d.c. voltage.

5. Multimeter can be used as an ammeter by ________
a) connecting series resistances
b) making use of a transducer
c) making use of a transformer
d) connecting shunts

View Answer

Answer: d [Reason:] An electronic multimeter can be used as an ammeter by making use of shunt resistances across the meter. This is achieved by range selecting switch.

6. Multimeter can be used for D.C. voltage measurement by ________
a) connecting series resistances
b) connecting shunt resistances
c) connecting star delta resistances
d) using a switch

View Answer

Answer: a [Reason:] We can obtain a wide range of D.C. voltage from a multimeter by connecting various series resistances in the circuit through a range selection switch. By adjusting the value of the resistance we get the required D.C. voltage.

7. Multimeter can be used only for low resistance measurement.
a) True
b) False

View Answer

Answer: b [Reason:] A multimeter is used for the measurement of A.C. as well as D.C. voltage, current and resistance. By manipulating the scale with a multiplication factor of 100 and 10, 000 we can make use of a multimeter for measuring high resistances.

8. What is the role of a rectifier in a multimeter?
a) bias purpose
b) thermal stability
c) rectification
d) inversion

View Answer

Answer: c [Reason:] When the multimeter is used for the measurement of A.C. voltages, rectifier section is used. It mainly performs the conversion of the input A.C. voltage into D.C. for the measurement of A.C. voltage.

9. What is the initial setting made in a multimeter before it is used for measuring resistance?
a) fine adjustment
b) instrument is open circuited
c) voltage is applied
d) zero adjustment

View Answer

Answer: d [Reason:] Initially the multimeter is short circuited and zero adjustment control is made. This is done till the meter reads zero resistance or in other words displays full scale current.

Set 3

1. Magnitude of flux in an energy meter varies __________
a) due to abnormal currents and voltages
b) due to high resistance and inductance values
c) due to change in the transformer turns
d) due to the induced e.m.f in the windings

View Answer

Answer: a [Reason:] In the driving system of an energy meter, magnitude of flux can be incorrect as a result of abnormal values of currents and voltages. This occurs due to change in the resistance of the pressure coil circuit.

2. Phase angles in an energy meter cannot be incorrect.
a) True
b) False

View Answer

Answer: b [Reason:] In an energy meter, phase angle errors occur as a result of improper adjustments of lag condition, abnormal frequencies etc,. Due to temperature, changes in resistance values also lead to error in the phase angle.

3. Energy meter creeps __________
a) due to change in supply
b) due to reversal in polarity of voltage
c) due to asymmetry in magnetic circuit
d) due to turns ratio of transformer

View Answer

Answer: c [Reason:] In an energy meter, when the magnetic circuit is asymmetrical, a driving torque is produced. As a result of this driving torque, the energy meter creeps.

4. Supply voltage in an energy meter is __________
a) constant always
b) zero always
c) depends on the load
d) can fluctuate

View Answer

Answer: d [Reason:] Generally the supply voltage is constant in an energy meter. It can fluctuate as a result of unavoidable reasons leading to errors in the reading of the energy meter.

5. How is the flux of shunt coil related to voltage?
a) flux is proportional to square of voltage
b) directly proportional
c) inversely proportional
d) independent of each other

View Answer

Answer: a [Reason:] In an energy meter, the supply voltage may fluctuate as a result of unavoidable reasons leading to errors in the reading. Supply voltage causes the shunt flux to induce an e.m.f in the disc. This is results in a self braking torque proportional to square of the voltage.

6. How can temperature effect be compensated in an energy meter?
a) through heat sinks
b) by a temperature shunt
c) by using resistance
d) by using a coolant

View Answer

Answer: b [Reason:] The resistance of the copper and aluminium parts in an energy meter increase with an increase in the temperature. As a result the disc rotates with a speed that is higher than actual. Temperature effects can be compensated by making use of a temperature shunt on the brake magnet.

7. Disc rotates slowly in some energy meters.
a) True
b) False

View Answer

Answer: a [Reason:] Even when there is no current flow through the energy meter, disc rotates slowly. This is known as creeping. This is occurs as a result of the over compensation provided for friction.

8. Creeping is avoided by __________
a) reversing the polarity of the voltage
b) drilling two diametrically opposite holes
c) holding the disc
d) increasing the friction

View Answer

Answer: b [Reason:] In an energy meter, creeping causes the disc to rotate even when there is no current flowing. By drilling two diametrically opposite holes under the edge of the poles of a shunt magnet, rotation of the disc is limited to a minimum value.

9. In some energy meters, creeping can be avoided by __________
a) attaching small gold pieces
b) attaching small aluminium pieces
c) attaching small iron pieces
d) attaching small zinc pieces

View Answer

Answer: c [Reason:] By attaching some iron pieces to the edge of the disc, creeping can be limited in some energy meters. Force of attraction that is experienced by the brake magnet as a result of the iron piece is enough to eliminate the creeping.

Set 4

1. An electronic energy meter makes use of ___________
a) IC
b) Transformer
c) CRO
d) Multimeter

View Answer

Answer: a [Reason:] Basically, integrated circuits also known as IC’s are used for the operation of an electronic energy meter.

2. Measurement of energy involves _________
a) inductance and capacitance measurement
b) power consumption and time duration
c) resistance measurement and voltage drop
d) current consumption and voltage drop

View Answer

Answer: b [Reason:] An electronic energy meter is used in two stages. Energy measurement basically involves measurement of power and the time duration. In the first stage, it is used as a wattmeter while in the second stage it is used monitoring the power consumed in a time interval.

3. Average power is _________
a) product of voltage and current
b) product of average current and voltage
c) product of instantaneous voltage and current
d) product of absolute voltage and current

View Answer

Answer: c [Reason:] The average power is computed as the product of the instantaneous voltage across the load and the instantaneous current flowing through the load. A scaling device is used to bring the supply voltage to a proper level.

4. What is the role of a multiplier?
a) it multiplies the voltage and current
b) divides the alternating voltage and current
c) supplies instantaneous voltage and current
d) multiplies alternating voltage and current

View Answer

Answer: d [Reason:] A multiplier basically performs the multiplication of the alternating voltage and the current. Multiplier also provides the current in the form of instantaneous power to a voltage controlled oscillator.

5. Frequency of oscillation in an electronic energy meter depends on
a) output current of multiplier
b) output voltage of multiplier
c) output power of multiplier
d) input resistance of multiplier

View Answer

Answer: a [Reason:] Oscillator used in an energy meter generates a square wave. The frequency of the this depends on the output current flowing through the multiplier.

6. Analog signal is converted _________
a) into oscillations
b) into digital
c) into pulses
d) into current

View Answer

Answer: b [Reason:] The analog signal obtained in an electronic energy meter is converted into digital by making use of a digital circuit. By making use of a seven-segment display, energy is mentioned in watt-hours.

7. An electronic energy meter is advantageous compared to conventional ones.
a) True
b) False

View Answer

Answer: a [Reason:] An electronic energy meter does not have frictional losses, creeping is not needed irrespective of the nature of the load such as low load, full load power factor etc., and the accuracy in the reading is of the order of ±1%.

8. Energy meter can be directly used in measurement.
a) True
b) False

View Answer

Answer: b [Reason:] Adjustments need to be made in an energy meter before it is used for the measurement of energy. This is done in order to keep the errors due to measurement within allowable limits of ±5 %.

9. Creeping in an energy meter can be found using _________
a) creep adjustment
b) preliminary light load adjustment
c) full load u.p.f adjustment
d) light load adjustment

View Answer

Answer: b [Reason:] Energy meter can be tested for creeping using preliminary light load adjustment. Disc holes are so positioned that they aren’t under the poles of a series magnet.

10. Preliminary light load adjustment involves _________
a) applying rated voltage across current coil
b) making use of a light load
c) applying rated voltage across pressure coil
d) adjusting the light load

View Answer

Answer: c [Reason:] Rated voltage is applied across the pressure coil. No current flows through the current coil. Till the disc stops rotating, light load device or equipment is adjusted continuously.

11. Creep adjustment involves _________
a) adjusting the creep
b) exciting the current coil
c) adjusting the turns ratio
d) exciting the pressure coil

View Answer

Answer: d [Reason:] The pressure coil is excited by 110% with respect to the rated voltage. Load current is zero. The meter will not creep provided the light load is adjusted correctly.

12. Light load adjustment involves _________
a) applying rated voltage across the pressure coil
b) adjusting a light load
c) applying rated current across the transformer
d) applying rated voltage across the current coil

View Answer

Answer: a [Reason:] Disc rotation is adjusted in such a way that correct speed is maintained. The pressure coil is supplied with the rated voltage and the current coil is provided with only about 5 % of the full load at u.p.f.

13. Low power factor adjustment involves _________
a) adjusting the power factor at lower loads
b) applying rated voltage to pressure coil and a p.f. of 0.5 for current coil
c) only applying rated voltage to pressure coil
d) only a p.f. of 0.5 for the current coil

View Answer

Answer: b [Reason:] Rated voltage is applied to the pressure coil. The current coil is provided with a current at 0.5 p.f. lagging. Till the disc rotates at correct speed, lag device is adjusted.

14. Full load u.p.f adjustment involves _________
a) adjusting the loads at unity power factor
b) applying rated voltage to pressure coil and a p.f. of unity for current coil
c) only applying rated voltage to pressure coil
d) only a p.f. of unity for the current coil

View Answer

Answer: c [Reason:] Rated voltage is applied to the pressure coil. The current coil is provided with a current at unity p.f. Errors are kept minimum and the position of the brake magnet is so adjusted that disc rotates at correct speed.

Set 5

1. Energy meter reads correctly when
a) torque is small
b) torque is large
c) torque is medium
d) torque is zero

View Answer

Answer: a [Reason:] The reading in an energy meter is obtained correctly when the torque value is small at low loads. It is independent of the load on the meter an acts in the same direction as the driving torque.

2. Small torque for energy meter is provided
a) by a supply
b) by a shading loop
c) by unshaded loop
d) by a transformer

View Answer

Answer: b [Reason:] Friction can be compensated in an energy meter by making use of a shading loop. It is placed between the central limb of the shunt magnet and a disc. Figure below illustrates the same. electrical-measurements-questions-answers-friction-overload-compensation-q2

3. Driving torque is small and is adjustable.
a) True
b) False

View Answer

Answer: a [Reason:] Interaction between the parts of the shaded and unshaded fluxes, obtained through a shading loop leads to a small driving torque. The value of the torque can be adjusted through lateral movement of the loop.

4. Friction torque is eliminated by _________
a) using lubricating oil
b) by suspending the components in air
c) by adjusting position of limb
d) by using steel alloy components

View Answer

Answer: c [Reason:] We can eliminate the friction torque completely by adjusting the position of the shading loop. This enables in providing compensation for the frictional torque.

5. Frictional errors are dominant in an energy meter.
a) True
b) False

View Answer

Answer: a [Reason:] Frictional errors exist in an energy meter at the top as well as bottom surfaces even at low value of loads. Even when the disc is rotating slowly errors due to friction exist in an energy meter.

6. At full load, disc
a) partially revolves and then stops
b) continuously revolves
c) does not revolve at all
d) revolves in an alternating fashion

View Answer

Answer: b [Reason:] When an energy meter is operated in full load condition, disc revolves continuously due to the field of the series magnet. As a result, an e.m.f is induced in the disc.

7. Self braking torque is _________
a) proportional to cube of load current
b) proportional to load current
c) proportional to square of load current
d) proportional to reciprocal of load current

View Answer

Answer: c [Reason:] In an energy meter, the self braking torque is dependent on the square of the load current. As a result the disc rotates at a slightly slower speed at high value of loads.

8. Self braking action is minimised by _________
a) maintaining high speed for disc
b) maintaining medium speed for disc
c) keeping the disc at rest
d) maintaining low speed for disc

View Answer

Answer: d [Reason:] In an energy meter we can minimise or eliminate the self braking action by keeping the disc speed as low as possible at full load condition. This is achieved by maintaining the flux due to the current coil smaller than that due to the shunt coil. Figure below shows the compensating device. electrical-measurements-questions-answers-friction-overload-compensation-q8

9. Overload compensating devices is _________
a) in the form of a magnetic shunt
b) in the form of a series magnet
c) in the form of a transformer
d) in the form of a supply

View Answer

Answer: a [Reason:] Magnetic shunt reaches saturation at overloads. As a result, its permeability reduces. Hence the overload compensating device takes the form of a magnetic shunt.