This set of Basic Electrical Engineering Questions and Answers for Entrance exams focuses on “Average and r.m.s. Values of Sinusoidal Currents and Voltages”.

1. RMS stands for ____________

a) Root Mean Square

b) Root Mean Sum

c) Root Maximum sum

d) Root Minimum Sum

View Answer

Explanation: RMS stands for Root Mean Square. This value of current is obtained by squaring all the current values, finding the average and then finding the square root.

2. If Im is the maximum value of a sinusoidal voltage, what is the instantaneous value?

a) i=Im/2

b) i=Imsinθ

c) i=Imcosθ

d) i=Im

View Answer

Explanation: The instantaneous value of a sinusoidal varying current is i=Imsinθ , where theta is the angle from instant of zero current.

3. In a sinusoidal wave, average current is always _______ rms current.

a) Greater than

b) Less than

c) Equal to

d) Not related

View Answer

Explanation: The average value of current is the sum of all the currents divided by the number of currents whereas RMS current is obtained by squaring all the current values, finding the average and then finding the square root. Hence RMS current is greater than average current.

4. Average value of current over a half cycle is?

a) 0.67Im

b) 0.33Im

c) 6.7Im

d) 3.3Im

View Answer

Explanation: Integrating idθ in the interval from 0 to pi ( since we are finding the average current over one half cycle) , we get i=0.61Im.

5. Find the average value of current when the current that are equidistant are 4A, 5A and 6A.

a) 5A

b) 6A

c) 15A

d) 10A

View Answer

Explanation: The average value of current is the sum of all the currents divided by the number of currents. Therefore average current= (5+4+6)/3=5A.

6. What is the correct expression for the rms value of current?

a) Irms=Im/2

b) Irms=Im/√2

c) Irms=Im/4

d) Irms=Im

View Answer

The correct expression for the rms value of current is Irms= Im/√2, where Im is the maximum or peak value of the current.

7. __________ current is found by dividing the area enclosed by the half cycle by the length of the base of the half cycle.

a) RMS current

b) Average current

c) Instantaneous current

d) Total current

View Answer

Explanation: The average value of current is the sum of all the currents divided by the number of currents. Hence it can also be found by dividing the area enclosed by the half cycle by the length of the base of the half cycle.

8. Peak value divided by the rms value gives us?

a) Peak factor

b) Crest factor

c) Both peak and crest factor

d) Neither peak nor crest factor

View Answer

Explanation: Peak and crest factor both mean the same thing. Hence the peak value divided by the rms value gives us the peak or crest factor.

9. What is the effective value of current?

a) RMS current

b) Average current

c) Instantaneous current

d) Total current

View Answer

Explanation: Effective current is also known as the effective current. RMS stands for Root Mean Square. This value of current is obtained by squaring all the current values, finding the average and then finding the square root.

10. What is the type of current obtained by finding the square of the currents and then finding their average and then fining the square root?

a) RMS current

b) Average current

c) Instantaneous current

d) Total current

View Answer

Explanation: RMS stands for Root Mean Square. This value of current is obtained by squaring all the current values, finding the average and then finding the square root.

**Sanfoundry Global Education & Learning Series – Basic Electrical Engineering.**

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