This Portion of Electrical andElectronic Measurements and Measuring instruments contains Potentiometers MCQs (Multiple Choice Questions and Answers) / Objective Type Questions and Answers.

This Section covers below lists of topics.

  1. Types of Potentiometer
  2. Self-balancing Potentiometers
  3. A.C Potentiometers

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1. A potentiometer is basically a :

  • Deflection type instrument
  • Null type instrument
  • Deflection as well as null type instrument
  • A digital instrument

2. When a potentiometer is used for measurement of voltage of an unknown source , the power consumed in the circuit of the unknown source under null conditions

  • Is very high
  • Is high
  • Is small
  • Is ideally zero

3. Standardization of potentiometers is done in order that, they become

  • Accurate
  • Precise
  • Accurate and direct reading
  • Accurate and precise.

4. A Crompton’s Potentiometer is provided with a dial resistor having 15 steps of 10Ω each and a slide wire of 10 Ω resistances the slide wire is divided into 100 divisions and one fifth of a division can be read with certainty. The working current of potentiometers is 10mA. The range and resolution of the potentiometer are respectively :

  • 1.6 V, 0.2 mV
  • 1.6 V, 0.5 mV
  • 1.5 V, 0.1 mV
  • 1.6 V, 0.1 mV

5. A dual range Crompton’s potentiometer is provided with a dial resistor having 15 steps of 10 Ω each and a slide wire of 10 Ω resistances. The ranges are X1 and X0.1. The current in the potentiometer measuring circuit 10mA on the X1 scale. The slide wire has 100 divisions and one fifth of a scale division can be read with certainty. What is the current drawn from the battery and the resolution of the instrument on X0.1 scale range?

  • 10mA, 20µV
  • 11mA, 10µV
  • 11mA, 2µV
  • 11mA, 20µV

6. Brook’s deflectional potentiometer is used when the unknown voltage :

  • Is constant
  • Is varying at slow rate
  • Is varying very rapidly
  • All the above.

7. A volt-ratio box is designed with a resistance 100 Ω/V. it has input terminals of 300V, 150V and 75 V, and an output terminal of 1.5 V which is connected to the potentiometer. Supposing a voltage of 270V is connected to the 300 V terminals, what is voltage indicated by the potentiometer and what is the power consumption under null conditions?

  • 1.5 V, 3W
  • 1.35 V, 3W
  • 1.5 V,2.43W
  • 1.35 V, 2.43W.

8. The standardization of a.c potentiometer is done by

  • Directly using a.c standard voltage source
  • Using d.c standard sources and transfer instruments
  • Using d.c standard sources and d’Arsonval galvanometer
  • Using a.c standard sources and transfer instruments.

9. The reading of polar type a.c potentiometer when measuring the reactance of a coil are I = 12 ∠13.8° , V =27.8 ∠29.7°. The reactance of the coil is :

  • 2.317Ω
  • 0.634 Ω
  • 2.22 Ω
  • -2.22 Ω

10. A Coordinate type potentiometer is used for determination of impedance of a coil and the results obtained are: voltage across 1Ω resistance in series with coil, 0.24 V on in phase dial and -0.09 on quadrature dial. The resistance of the coil is:

  • 9.14 Ω
  • 2.34 Ω
  • 16.76 Ω
  • None of the above.

11. The transfer instrument which is used for standardisation of a polar-type ac potentiometer is

  • an electrostatic instrument
  • a dynamometer instrument
  • a moving coil instrument
  • a thermal instrument

12. A dc potentiometer is designed to measure up to about 2 volts with a slide wire of 800 mm. A standard cell of emf 1.18 volt obtains balance at 600 mm. a test cell is seen to obtained balance at 680 mm. The emf of the test cell is

  • 1.50 volts
  • 1.00 volts
  • 1.34 volts
  • 1.70 volts

13. For measuring an ac voltage by an ac potentiometer, it is desirable that the supply for the potentiometer is taken from

  • a battery
  • the same source as the unknown voltage
  • a source other than the source of unknown voltage
  • any of the above

14. The calibration of a voltmeter can be carried out by using

  • an ammeter
  • a function generator
  • a frequency meter
  • a potentiometer

15. A slide wire potentiometer has 10 wires of 1 m each. With the help of a standard voltage source of 1.018 volt it is standardise by keeping the jockey at 101.8 cm. If the resistance of the potentiometer wire is 1000 Ω then the value of the working current is

  • 1 mA
  • 0.5 mA
  • 0.1 A
  • 10 mA

16. The potentiometer is standardised for making it

  • precise
  • accurate
  • accurate and precise
  • accurate and direct reading

17. Consider the following statements.A dc potentiometer is the best means available for the measurement of dc voltage because  
  1. The precision in measurement is independent of the type of detector used
  2. It is based on null balance technique
  3. It is possible to standardize before a measurement is undertaken
  4. It is possible to measure dc voltages ranging in value from mV to hundreds of volts Of these statements,

  • 2 and 3 are correct
  • 1 and 4 are correct
  • 2 and 4 are correct
  • 3 and 4 are correct

18. In a dc potentiometer measurements, a second reading is often taken after reversing the polarities of dc supply and the unknown voltage, and the average of the two readings is taken. This is with a view to eliminate the effects of

  • ripples in the dc supply
  • stray magnetic field
  • stray thermal emfs
  • erroneous standardisation

 

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