Electrical Instruments MCQ Questions & Answers

Electrical Instruments MCQs : This section focuses on the "Electrical Instruments". These Multiple Choice Questions (MCQs) should be practiced to improve the Electrical Instruments skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

A 0-400V voltmeter has a guaranteed accuracy of 1% of full scale reading. The voltage measured by this instrument is 250 V. Calculate the limiting error in percentage.

A. 4%
B. 2%
C. 2.5%
D. 1%

Question 2

A 500 A, 50 Hz current transformer has a bar primary. The secondary burden is a pure resistance of 1 ? and it draws a current of 5 A. If the magnetic core requires 250 Ampere-turn for magnetization, the percentage ratio error is __________

A. 10.56%
B. -10.56%
C. 11.80%
D. -11.80%

Question 3

A resistor of 10 k? with the tolerance of 5% is connected in parallel with 5 k? resistors of 10% tolerance. What is the tolerance limit for a parallel network?

A. 9%
B. 12.4%
C. 8.33%
D. 7.87%

Question 4

A resistor of 10 k? with the tolerance of 5% is connected in series with 5 k? resistors of 10% tolerance. What is the tolerance limit for a series network?

A. 9%
B. 12.04%
C. 8.67%
D. 6.67%

Question 5

A voltmeter has a sensitivity of 1000 ?/V reads 200 V on its 300 V scale. When connected across an unknown resistor in series with a millimeter. When the milliammeter reads 10 mA. The actual resistance of the unknown resistor will be?

A. 20 k?
B. 18.57 k?
C. 21.43 k?
D. 22.76 k?

Question 6

A voltmeter has a sensitivity of 1000 ?/V reads 200 V on its 300 V scale. When connected across an unknown resistor in series with a millimeter. When the milliammeter reads 10 mA. The apparent resistance of the unknown resistor will be?

A. 20 k?
B. 21.43 k?
C. 18.57 k?
D. 22.36 k?

Question 7

A voltmeter has a sensitivity of 1000 ?/V reads 200 V on its 300 V scale. When connected across an unknown resistor in series with a millimeter. When the milliammeter reads 10 mA. The error due to the loading effect of the voltmeter is ________

A. 3.33%
B. 6.67%
C. 13.34%
D. 13.67%

Question 8

Resistances R1 and R2 have respectively, nominal values of 10? and 5? and limiting error of ± 5% and ± 10%. The percentage limiting error for the series combination of R1 and R2 is?

A. 6.67%
B. 5.5%
C. 7.77%
D. 2.8%

Question 9

The current flowing in a resistor of 1? is measured to be 25 A. But it was discovered that ammeter reading was low by 1% and resistance was marked high by 0.5%. Find true power as a percentage of the original power.

A. 95%
B. 101.5%
C. 100.1%
D. 102.4%

Question 10

Two resistances 100 ± 5? and 150 ± 15? are connected in series. If the error is specified as standard deviations, the resultant error will be _________

A. ±10 ?
B. ±10.6 ?
C. ±15.8 ?
D. ±20 ?

Question 11

A 0-400V voltmeter has a guaranteed accuracy of 1% of full scale reading. The voltage measured by this instrument is 250 V. Calculate the limiting error in percentage.

A. 4%
B. 2%
C. 2.50%
D. 1%

Question 12

A 500 A, 50 Hz current transformer has a bar primary. The secondary burden is a pure resistance of 1 Ω and it draws a current of 5 A. If the magnetic core requires 250 Ampere-turn for magnetization, the percentage ratio error is __________

A. 10.56%
B. -10.56%
C. 11.80%
D. -11.80%

Question 13

A resistor of 10 kΩ with the tolerance of 5% is connected in parallel with 5 kΩ resistors of 10% tolerance. What is the tolerance limit for a parallel network?

A. 9%
B. 12.40%
C. 8.33%
D. 7.87%

Question 14

A voltmeter has a sensitivity of 1000 Ω/V reads 200 V on its 300 V scale. When connected across an unknown resistor in series with a millimeter. When the milliammeter reads 10 mA. The actual resistance of the unknown resistor will be?

A. 20 kΩ
B. 18.57 kΩ
C. 21.43 kΩ
D. 22.76 kΩ

Question 15

A voltmeter has a sensitivity of 1000 Ω/V reads 200 V on its 300 V scale. When connected across an unknown resistor in series with a millimeter. When the milliammeter reads 10 mA. The apparent resistance of the unknown resistor will be?

A. 20 kΩ
B. 21.43 kΩ
C. 18.57 kΩ
D. 22.36 kΩ

Question 16

A voltmeter has a sensitivity of 1000 Ω/V reads 200 V on its 300 V scale. When connected across an unknown resistor in series with a millimeter. When the milliammeter reads 10 mA. The error due to the loading effect of the voltmeter is ________

A. 3.33%
B. 6.67%
C. 13.34%
D. 13.67%

Question 17

Resistances R1 and R2 have respectively, nominal values of 10Ω and 5Ω and limiting error of ± 5% and ± 10%. The percentage limiting error for the series combination of R1 and R2 is?

A. 6.67%
B. 5.50%
C. 7.77%
D. 2.80%

Question 18

The current flowing in a resistor of 1Ω is measured to be 25 A. But it was discovered that ammeter reading was low by 1% and resistance was marked high by 0.5%. Find true power as a percentage of the original power.

A. 95%
B. 101.50%
C. 100.10%
D. 102.40%