# RMS Value of Sinusoidal Current and Voltage MCQ [Free PDF]

1. If the maximum value of current is 5√2 A, what will be the value of RMS current?

A. 10 A
B. 5 A
C. 15 A
D. 25 A

We know, the value of RMS current = value of max current/√2

Substituting the value of max current we get, RMS current = 5A.

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 = Imsinθ or i = Imcosθ

The instantaneous value of a sinusoidally varying current is

i = Imsinθ or i = Imcosθ

where Im is the maximum value of current.

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

A. 0.67Im
B. 0.33Im
C. 6.7Im
D. 3.3Im

Average current = ∫0πidθ/π

= ∫0πImsinθ dθ/π = 2Im/π = 0.67 Im.

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

Irms2  = ∫0πdθ i2/2π = Im2/2

Irms = Im/√2.

5. Average value of current over a full cycle is?

A. 0.67Im
B. 0
C. 6.7Im
D. 3.3Im

The average of sine or cosine over a period is zero so, the average value of current over a full cycle is zero.

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

A. Irms × Iav
B. Irms / Iav
C. Irms + Iav
D. Irms – Iav

The correct expression for the form factor is Irms/Iav where Irms 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

For a direct current, the mean current value is the same as that of the RMS current.

8. For a direct current, the RMS voltage is ________ the mean voltage.

A. Greater than
B. Less than
C. Equal to
D. Not related to

For a direct current, the mean voltage value is the same as that of the RMS voltage.

9. What is the value of the form factor for the sinusoidal current?

A. π/2
B. π/4
C. 2π
D. π/√2

For sinusoidal current, Irms = Im/√2

Iav = √2 Im/π

So, form factor = Irms/Iav  = π/2.

10. If the maximum value of the current is 5√2 A, what will be the value of the average current?

A. 10/π A
B. 5/π A
C. 15/π A
D. 25/π A