1. Hot wire ammeters are used for measuring:
(a) Only a.c.
(b) Only d.c
(c) Neither a.c nor d.c
(d) Both a.c. and d.c.
Ans: d
2. Rectifier type instrument can be used in-
(a) a.c.
(b) d.c.
(c) Both (a) and (d)
(d) Pulsating
Ans: a
3.An electrodynamometer type of instruments finds its major use as
(a) Standard instrument only
(b) Transfer instrument only
(c) Both as or standard and transfer instruments
(d) An indicator type of instrument
Ans: c
4.Which one of the following instruments is equally accurate on ac as well as dc circuits?
(a) PMMC voltmeter
(b) Dynamometer wattmeter
(c) Moving iron ammeter
(d) Induction wattmeter
Ans: b
5.The ratio error in current transformer is due to:
(a) Power factor of primary
(b) Wattles component of the current in the primary
(c) Exciting currents
(d) Leakage flux
Ans: c
6.To minimize the errors due to lead and contact resistance, low resistance used in electrical measurement work are provided with
(a) Guard rings
(b) Four terminals
(c) Thick insulation
(d) Metal shields
Ans: b
7.A power factor meter has
a)One current circuit and two pressure circuits
b)One current circuit and one pressure circuit
c)Two current circuits and one pressure circuit
d)None of the above
Ans: a
8.In order to achieve accuracy, how should the slide wire of a
potentiometer be?
(a) As long as possible
(b) As short as possible
(c) Very thin
(d) Very thick
Ans: b
9.Torque/weight ratio of an instrument indicates:
(a) Selectivity
(b) Sensitivity
(c) Accuracy
(d) Fidelity
Ans: b
10.Energy meter runs slowly even if power is not used. This error is called
(a) Speed error
(b) Phase error
(c) Creeping error
(d) None of these
Ans: c
11.A null type of instrument as compared to a deflecting type instrument has
(a) Higher accuracy
(b) Lower sensitivity
(c) Faster response
(d) All of the above
Ans: a
12. A 0-10 A ammeter has a guaranteed accuracy of 1% of full-scale deflection, the limiting error while reading 2.5A will be
(a) 1%
(b) 2%
(c) 4%
(d) None of these
Ans: c
13. Indicating instruments should be
(a) Undamped
(b) Critical damped
(c) Over damped
(d) Under damped
Ans: b
Note: Practical indicating instruments generally are Under damped, but in this question, it asked for ideal case therefore correct answer is critical damped
14. The effect of stray magnetic fields on the actuating torque of a portable instrument is the maximum when the operating field of the instrument and the stray fields are
(a) Perpendicular
(b) Parallel
(c) Inclined at 60 degree
(d) Inclined at 30 degree
Ans: b
15. In a particular meter, the operating torque is directly proportional to the current passing through it, then the type of meter is:
(a) Moving iron
(b) Moving coil
(c) Electrostatic
(d) Induction
Ans: b
16.A moving iron instrument can be used for current and voltage measurements?
(a) In AC circuit only
(b) In DC circuits only
(c) In both AC and DC circuit
(d) None of these
Ans: c
17. A 0-1 mA PMMC ammeter reads 4 mA in circuits. Its bottom control spring snaps suddenly. The meter will now read nearly: (a) Zero
(b) 10 mA
(c) 2 mA
(d) 8 mA
Ans: a
18.Which torque is essential for indicating instruments-?
(a) Deflecting
(b) Controlling
(c) Damping
(d) All of the above
Ans: d
19. Moving coil instruments have which one of the following scales? (a) Logarithmic scale
(b) Uniform scale
(c) Non-uniform scale
(d) Squared scale
Ans: b
20.The material of hair spring used in measuring instruments is made of which of material of the following:
(a) Copper
(b) Bronze
(c) Alnico
(d) None of these
Ans: b
21.Swamping resistance is used to compensate error due to-
(a) Stray magnetic field
(b) Large supply voltage
(c) Large supply frequency
(d) Temperature variations
Ans: d
22.Which of the following instruments has the highest torque/weight ratio among the given instruments?
(a) Attraction type MI instrument
(b) Repulsion type MI instrument
(c) Permanent magnet moving coil instrument
(d) Electrodynamometer instrument
Ans: c
23.The measurement range of an ammeter can be increased by using a:
(a) High resistance in shunt
(b) Low resistance in shunt
(c) High resistance in series
(d) Low resistance in series
Ans: b
24.To increasing the range of an a.c. ammeter you would use:
(a) A potential transformer
(b) An inductance across the motor
(c) A condenser across the meter
(d) Current transformer
Ans: b
25.Which damping is most efficient-?
(a) Air friction
(b) Fluid friction
(c) Eddy current
(d) None of the above
Ans: c
26.Two voltmeter of (0-300 V) range are connected in parallel to a.c. circuits. One voltmeter is moving iron type reads 200 V. If the other is PMMC instrument, its riding will be:
(a) Zero
(b) 222 V
(c) 127.4 V
(d) Slightly less 200 V
Ans: a
27.A standard cell of 1.0185 V is used with a slide wire potentiometer. The balance was obtained at 60 cm. When an unknown emf was connected, the balance was obtained at 82 cm. What is the magnitude of unknown emf?
(a) 1.39 V
(b) 0.79 V
(c) 13.9 V
(d) 7.45 V
Ans: a
28.Clamp on ammeter is used for measurement of:
(a) Large alternating currents
(b) Small direct currents
(c) Small alternating currents
(d) Large direct currents
Ans: a
29.The multiplying power of the shunt of a millimeter is 8. If the circuit current is 200 mA. Then current through the meter us
(a) 25 mA
(b) 200 mA
(c) 1600 mA
(d) 3200 mA
Ans: a
30.A DC ammeter has a resistance of 0.1Ω and current range is 0 – 100A. If the range is to be extended to 0- 500A, then meter enquires shunt resistance of: (a) 0.010Ω
(b) 0.011Ω
(c) 0.025Ω
(d) 1.0Ω
Ans: c
“The Pessimist Sees Difficulty In Every Opportunity. The Optimist Sees Opportunity In Every Difficulty”
By-wiston churchill
For Explanation of each question you can watch this video..