R4RIN – MCQs, Mock Tests | Electrical measurements Electrical Measurement MCQ Question Set 5

The secondary circuit of a C.T. is open when?

1. a very high flux density is produced
2. a very low flux density is produced
3. a moderate flux density is produced
4. no flux density is produced

✅ Correct Answer: 1

High flux density leads to _____

1. a decreased voltage in the secondary
2. a decreased voltage in the primary
3. a increased voltage in the secondary
4. a decreased voltage in the primary

✅ Correct Answer: 3

When primary current flows, secondary circuit should be open.

1. True
2. False
3. all of the above
4. None of the mentioned

✅ Correct Answer: 2

High magnetizing forces in the core when removed suddenly lead to _____

1. no residue
2. partial residual magnetism
3. rupture of the device
4. residual magnetism

✅ Correct Answer: 4

The secondary winding of a C.T. ________

1. can be shorted
2. can’t be shorted
3. can be opened
4. can’t be opened

✅ Correct Answer: 1

The secondary winding of a C.T. is opened when?

1. C.T. is magnetised
2. C.T. is demagnetised
3. C.T. is shorted
4. C.T. is opened

✅ Correct Answer: 2

The rectangular type of C.T. is built of ______

1. L shaped windings
2. T shaped windings
3. A shaped windings
4. Z shaped windings

✅ Correct Answer: 1

Potential transformers are used to measure ______

1. high voltages
2. low voltages
3. high currents
4. low currents

✅ Correct Answer: 1

Potential transformers are used with ______

1. high range voltmeter
2. low range voltmeter
3. intermediate range voltmeter
4. very high range voltmeter

✅ Correct Answer: 2

Potential transformer is similar in design to a _____

1. C.T.
2. Step up transformer
3. Power transformer
4. Step down transformer

✅ Correct Answer: 3

The secondary winding of a P.T. is designed for ____

1. 220 V
2. 2.2 kV
3. 1.1 kV
4. 110 V

✅ Correct Answer: 4

The primary current in a C.T. is _____

1. independent of secondary circuit
2. dependent on the secondary circuit
3. depends on the transformation ratio
4. depends on the nominal ratio

✅ Correct Answer: 1

The excitation current of a C.T. ______

1. varies over a fixed range of operation
2. varies over a wide range of normal operation
3. is fixed over a range of operation
4. is fixed always

✅ Correct Answer: 2

Secondary of a P.T. can be open circuited.

1. True
2. False
3. all of the above
4. None of the mentioned

✅ Correct Answer: 1

When C.T. is connected in series with a line, a large voltage exists across the primary.

1. True
2. False
3. all of the above
4. None of the mentioned

✅ Correct Answer: 2

Winding resistance of a P.T. can be reduced by ______

1. using thick conductors
2. decreasing the length of the winding
3. shorting the primary and secondary windings
4. using thin conductors

✅ Correct Answer: 1

Leakage reactance is minimised by _____

1. using thin conductors
2. reducing leakage flux
3. increasing flux density
4. shorting the windings

✅ Correct Answer: 2

High flux density is due to less turns.

1. True
2. False
3. all of the above
4. None of the mentioned

✅ Correct Answer: 1

Ratio error in a P.T. depends on _____

1. secondary current
2. primary voltage
3. secondary current
4. turns ratio

✅ Correct Answer: 3

In a P.T. values of components of currents are negligible.

1. True
2. False
3. all of the above
4. None of the mentioned

✅ Correct Answer: 2

Ratio error can be minimised by _____

1. reducing the turns
2. reducing the current
3. increasing the voltage
4. using a good core material

✅ Correct Answer: 4

Another method of eliminating the ratio error is _____

1. by reducing secondary turns
2. by increasing the primary turns
3. by increasing secondary turns
4. by reducing the primary turns

✅ Correct Answer: 1

Increasing secondary burden _______

1. increases Is
2. decreases Is
3. keeps Is constant
4. decreases Ip

✅ Correct Answer: 1

For a given Vp the Vs ___

1. increases
2. decreases
3. remains constant
4. depends on the supply

✅ Correct Answer: 2

What is effect of the secondary burden on the ratio error?

1. ratio error is constant with secondary burden
2. ratio error decreases with secondary burden
3. ratio error increases with secondary burden
4. depends on the supply voltage

✅ Correct Answer: 3

Vp is leading in phase, while Vs is lagging in phase.

1. True
2. False
3. all of the above
4. None of the mentioned

✅ Correct Answer: 1

What is the effect of p.f. on secondary burden?

1. Ip shifts towards Io
2. Ip deviates from Io
3. Ip is independent of Io
4. Ip and Io cancel eachother

✅ Correct Answer: 1

How is the transformation ratio dependent on the secondary burden?

1. decreases
2. increases
3. remains constant
4. depends on the supply

✅ Correct Answer: 2

In a moving iron meter, the deflection torque is proportional to?

1. In a moving iron meter, the deflection torque is proportional to?
2. Current through the coil
3. Sine of measurand
4. The Square root of the measurand

✅ Correct Answer: 1

The full-scale deflection current of an ammeter is 4 mA and its internal resistance is 400Ω. If this meter is to have a full deflection of 10 A, what is the value of the shunt resistance to be used?

1. 49.99 Ω
2. 0.16 Ω
3. 1.5 Ω
4. 2.6 Ω

✅ Correct Answer: 2

The full-scale deflection current of a meter is 4 mA and its internal resistance is 400Ω. This meter is to have full deflection when 400 V is measured. What is the value of the series resistor to be used?

1. 99.90 kΩ
2. 100 kΩ
3. 99.60 kΩ
4. 100 Ω

✅ Correct Answer: 3

Two ammeters, one with a full-scale current of 1 mA and internal resistance of 100 Ω and other a full-scale current of 10 mA and internal resistance of 25 Ω are in parallel. What is the total current, these two meters can carry without the reading out of scale in any meter?

1. 1 mA
2. 10 mA
3. 11 mA
4. 5 mA

✅ Correct Answer: 4

A meter has a full scale of 90° at a current of 1 A. This meter has a perfect square law response. What is the current when the deflection angle is 45°?

1. 0.5 A
2. 0.25 A
3. 0.707 A
4. 0.67 A

✅ Correct Answer: 3

The scale of a dynamometer type instrument marked in terms of RMS value would be_____

1. Uniform throughout
2. Non-uniform and crowded near the full scale
3. Non-uniform and crowded near the full scale
4. Non-uniform and crowded around mid-scale

✅ Correct Answer: 3

Moving Iron Instrument can be used as _______

1. An ammeter for measuring DC as well as AC
2. For measuring DC current and voltages only
3. For measuring DC current and voltages only
4. For measuring AC current and voltages only

✅ Correct Answer: 3

A 10 mA PMMC ammeter reads 4 mA in a circuit. Its bottom control spring snaps suddenly. The meter will now show ______

1. 10 mA
2. 8 mA
3. 2 mA
4. Zero

✅ Correct Answer: 4

The standardization of AC potentiometer is done by _____

1. Using a DC standard source and d’ Arsonval galvanometer
2. Using AC standard sources and transfer instruments
3. Using a standard AC voltage source
4. Using a DC standard source and transfer instruments

✅ Correct Answer: 4

The inductance of a certain moving- iron ammeter is expressed as L = 10 + 3θ – θ24 μH, where θ is the deflection in radian from the zero position. The control spring torque is 25 × 10-6 Nm/rad. The meter carries a current of 5 A. What is the deflection?

1. 2.4
2. 2.0
3. 1.2
4. 1.0

✅ Correct Answer: 3

A current of – 8 + 6sqrt{2} (sin (ωt + 30°)) A is passed through three meters. The respective readings (in ampere) will be?

1. 8, 6 and 10
2. 8, 6 and 8
3. – 8, 10 and 10
4. -8, 2 and 2

✅ Correct Answer: 3

A rectifier type AC voltmeter consists of a series resistance R, an ideal full-wave rectifier bridge and a PMMC instrument. The internal resistance of the instrument is 100 Ω and a full- scale deflection is produced by a DC current of 1 mA. A voltage of 100 V (rms) is applied to the input terminals. The value of R required is?

1. 63.56 Ω
2. 89.83 Ω
3. 89.83 kΩ
4. 141.3 kΩ

✅ Correct Answer: 3

A current of [2 + 2–√ sin (314t + 30) + 22–√ cos (952t +45)] is measured with a thermocouple type, 5A full scale, class 1 meter. The meter reading would lie in the range?

1. 5 A ± 1 %
2. (2 + 32–√) A ± 1%
3. 3 A ± 1.7 %
4. 2 A ± 2.5 %

✅ Correct Answer: 3

A moving iron ammeter produces a full-scale torque of 240 μN-m with a deflection of 120° at a current of 10 A. the rate of change of self-inductance (μH/rad) of the instrument at full scale is?

1. 2.0 μH/rad
2. 4.8 μH/rad
3. 12.0 μH/rad
4. 114.6 μH/rad

✅ Correct Answer: 2

A moving coil of a meter has 250 turns and a length and depth of 40 mm and 30 mm respectively. It is positioned in a uniform radial flux density of 450 mT. The coil carries a current of 160 mA. The torque on the coil is?

1. 0.0216 N-m
2. 0.0456 N-m
3. 0.1448 N-m
4. 1 N-m

✅ Correct Answer: 1

Two 100 μA full-scale PMMC meters are employed to construct a 10 V and a 100 V full-scale voltmeter. These meters will have figure of merit (sensitivities) as?

1. 10 kΩ/V and 10 kΩ/V
2. 100 kΩ/V and 10 kΩ/V
3. 10 kΩ/V and 100 kΩ/V
4. 10 kΩ/V and 1 kΩ/V

✅ Correct Answer: 1

A PMMC rated as 100 μA is used in a rectifier type of instrument which uses full wave rectification. What is the sensitivity on sinusoidal AC?

1. 4.5 kΩ/V
2. 18 kΩ/V
3. 10 kΩ/V
4. 9 kΩ/V

✅ Correct Answer: 4

The discharge of a capacitor through a ballistic galvanometer produces a damped frequency of 0.125 Hz and successive swings of 120, 96 and 76.8 mm. The damping ratio is?

1. 0.0568
2. 0.0887
3. 0.0357
4. 0.0441

✅ Correct Answer: 3

The discharge of a capacitor through a ballistic galvanometer produces a damped frequency of 0.125 Hz and successive swings of 120, 96 and 76.8 mm. The logarithmic decrement is?

1. 0.225
2. 0.565
3. 0.484
4. 0.7887

✅ Correct Answer: 1

Power is ______

1. rate of doing work
2. rate of producing voltage
3. rate of generating current
4. rate of overcoming friction

✅ Correct Answer: 1

In A.C. circuits, power consumed is ________

1. product of voltage and current
2. it depends on the p.f. of the circuit in addition to voltage and current
3. it depends on the supply voltage
4. it depends on the magnitude of the circuit current

✅ Correct Answer: 2

In D.C. circuits, power is measured using ________

1. ohmmeter and galvanometer
2. ohmmeter and voltmeter
3. ammeter and voltmeter
4. ammeter and galvanometer

✅ Correct Answer: 3