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. If 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
View Answer
Explanation: We know, 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
View Answer
Explanation: The instantaneous value of a sinusoidal 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: Average of sine or cosine over a period is zero so, average value of current over 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
View Answer
Explanation: The correct expression for 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
View Answer
Explanation: 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
View Answer
Explanation: 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 sinusoidal current?
a) π/2
b) π/4
c) 2π
d) π/√2
View Answer
Explanation: 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
View Answer
Explanation: We know, the value of the average current = value of max current *√2 /π
Substituting the value of max current we get, rms current = 10/π A.
Sanfoundry Global Education & Learning Series – Basic Electrical Engineering.
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