This set of Basic Electrical Engineering Questions and Answers for Entrance exams focuses on “Average and RMS Values of Sinusoidal & Non-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 an instant of zero current.

3. 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.

4. 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

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

5. 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.

6. What is the correct expression for the form factor?

a) I*Iav

b) I/Iav

c) I+Iav

d) I-Iav

View Answer

Explanation: The correct expression for form factor is ki=I/Iav, where I is the rms value of the current and Iav is the average current.

7. For a direct current, the rms current is ________ the mean current.

a) Greater than

b) Less than

c) Equal to

d) Not related to

View Answer

Explanation: For a direct current, that is, a non-sinusoidal current, the mean current value is the same as that of the rms current.

8. For a direct voltage, the rms voltage is ________ the mean voltage.

a) Greater than

b) Less than

c) Equal to

d) Not related to

View Answer

Explanation: For a direct current, that is, a non-sinusoidal current, the mean voltage value is the same as that of the rms voltage.

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