Electrical & Electronic Measurements : 100 Most Important Questions with Solutions

1.The unit of solid angle is

Answer ||| C

Solution ||| The unit of solid angle is steradian. Radian is the SI unit for phase angles. Candela is the SI unit of luminous intensity.

2.A wattmeter has a current coil of 0.03 Ω resistance and a pressure coil of 4500 Ω resistance. The load voltage is 300 V and 0.6 power factor. What will be the value of load current when the error due to both connections will be equal?

Answer ||| B

Solution |||

The two possible connection is-

1) When a voltmeter is connected at the source end.

2) When a voltmeter is connected at the load end.

Error in connection (1) is-

I² × R_C

error in the connection (2) is-

= 

For equal error

I² × 0.03 = 

I = 25.81 A

3.The flux produced by shunt and series coil of the induction type instruments should be

Answer ||| A

Solution ||| When the angle between the shunt coil and the series coil is at a complementary angle i.e. 90 °, then the flux produced in the instrument is maximum.

4.A d.c voltmeter has a sensitivity of 1000 Ω / V. When it measures half of the full scale in 100 V range, the current through the voltmeter will be

Answer ||| B

Solution ||| Sensitivity of d.c. voltmeter = 100 Ω/volt
For half scale in 100 V range, i.e. 50 V current through the voltmeter,

5.Which of the following is the dimension of power?

A. 

B. 

C. 

D. 

Answer ||| A

Solution ||| The dimension of power is.

6.The AC Bridge used for measurement of dielectric loss of capacitor is

Answer ||| B

Solution ||| Schering Bridge is used for measurement of dielectric loss of capacitor.

7.Two holes are drilled in the disc on a diameter of the energy meter to

Answer ||| B

Solution ||| To eliminate the creeping on no-load condition two holes are drilled in the disc on a diameter of energy meter.

8.Which one of the following can act as an inverse transducer?

Answer ||| B

Solution ||| An inverse transducer converts electrical quantity into a non-electrical quantity.
Example: piezo-electrical crystal.

9.What is the purpose of aquadag in CRO?

Answer ||| B

Solution ||| Aquadag coating is used to collect secondary electrons emitted when the electron strikes the screen.

10.A single slide wire is used for the measurement of current in a circuit. The voltage drops across a standard resistance of 2 Ω is balanced at 70 cm. What is the magnitude of current if a standard cell having an emf of 1.8 V is balanced at 50 cm?

Answer ||| B

Solution |||

Since the standard cell is balanced at 70 cm.

i.e. 70 cm of wire has a resistance of 2 Ω.

So, the 50 cm of wire have resistance =  = 1.428 Ω

Since it is balanced by emf of 1.8V

So, V = IR

I =  = 1.26 A

11.For measuring current at the high frequency we should use

Answer ||| C

Solution |||

Thermocouple instruments are used at high frequency as their operation is based on heating effects and emf generation due to dissimilar conductor function.

12.A 0-20 mA PMMC ammeter reads 8 mA in a circuit. Its bottom control spring snaps suddenly. The meter will now read nearly

Answer ||| D

Solution ||| When the control spring breaks, the meter current flowing circuit gets open therefore the meter will read zero.

13.A resistance of 10 kΩ with 5 % tolerance is connected in series with 5 kΩ resistors of 10% tolerance. What is the tolerance limit for the series network?

Answer ||| B

Solution ||| Error in 10 kΩ resistance = 
Error in 5 kΩ resistance = 
Total measurement resistance = 10 + 5 + 0.5 + 0.5 = 16k

14.In 2-wattmeter method of measuring 3-ϕ power. Power factor is 0.5, then one of the wattmeter will read.

A. 

B. 

C. 

Answer ||| D

Solution ||| 

⇒ W₂ = 0

15.Which one of the types of standard resistance is the three-terminal type?

Answer ||| C

Solution ||| High resistance standard is “three-terminal type”
Guard terminal is used to avoid leakage current effect.

16.In MI meter the deflection torque is proportional to

Answer ||| A

Solution ||| The instrument in which the moving iron is used for measuring the flow of current or voltage is known as the moving iron instrument. It works on the principle that the iron place near the magnet attracts towards it. The force of attraction depends on the strength of the magnet field.

17.Which of the following is an integrating type instrument?

Answer ||| A

Solution ||| Energy meter is an integrating type instrument whereas voltmeter, ammeter and wattmeter are indicating type instruments.

18.Which one of the following does not employ a null method of measurement?

Answer ||| A

Solution ||| D.C. potentiometer, Kelvin double bridge and ac potentiometer employ a null method of measurement.

19.A dynamometer type instrument can be used on

Answer ||| C

Solution ||| A dynamometer type or electrodynamometer type instruments can work on both AC and DC.

PDF OF 100 MOST IMPORTANT QUESTIONS OF Electrical and Electronics Measurement 

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