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
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
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
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
High flux density is due to less turns.
1. True
2.False
3.all of the above
4.None of the mentioned
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
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
Potential transformers are used to measure ______
1.high voltages
2.low voltages
3.high currents
4. low currents
Potential transformers are used with ______
1. high range voltmeter
2.low range voltmeter
3. intermediate range voltmeter
4.very high range voltmeter
Ratio error can be minimised by _____
1.reducing the turns
2.reducing the current
3. increasing the voltage
4.using a good core material
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
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
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
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
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 %
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
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
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
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
For a given Vp the Vs ___
1. increases
2.decreases
3.remains constant
4.depends on the supply
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
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
How is the transformation ratio dependent on the secondary burden?
1.decreases
2. increases
3.remains constant
4.depends on the supply
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
In D.C. circuits, power is measured using ________
1. ohmmeter and galvanometer
2.ohmmeter and voltmeter
3.ammeter and voltmeter
4.ammeter and galvanometer
Increasing secondary burden _______
1. increases Is
2.decreases Is
3. keeps Is constant
4.decreases Ip
Leakage reactance is minimised by _____
1.using thin conductors
2.reducing leakage flux
3.increasing flux density
4.shorting the windings
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
Potential transformer is similar in design to a _____
1.C.T.
2.Step up transformer
3.Power transformer
4. Step down transformer
Power is ______
1.rate of doing work
2. rate of producing voltage
3.rate of generating current
4. rate of overcoming friction
Ratio error in a P.T. depends on _____
1.secondary current
2.primary voltage
3.secondary current
4. turns ratio
Secondary of a P.T. can be open circuited.
1.True
2.False
3.all of the above
4.None of the mentioned
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
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
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
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
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
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
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
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
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
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
The secondary winding of a P.T. is designed for ____
1.220 V
2.2.2 kV
3.1.1 kV
4. 110 V
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
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
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
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
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
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
When primary current flows, secondary circuit should be open.
1.True
2.False
3.all of the above
4.None of the mentioned