Engineering Questions with Answers - Multiple Choice Questions

# Basic Electrical Engineering MCQ’s – Alternating Current in a Capacitive Circuit

1 - Question

What is the resonance frequency of ac circuit?
a) 1/√LC
b) √(L/C)
c) √LC
d) LC

Explanation: At resonance, XL=XC
ωL=1/ωC
ω=1/√LC.

2 - Question

What is impedance at resonance?
a) maximum
b) minimum
c) zero
d) cannot be determined

Explanation: At resonance, XL=XC
Z2=R2+(XL-XC)2
Z=R So Z is minimum at resonance.

3 - Question

What is the value of impedance at resonance?
a) XL
b) XC
c) R
d) 0

Explanation: At resonance, XL=XC
Z2=R2+(XL-XC)2
Z=R So Z is minimum at resonance.

4 - Question

What is φ in terms of voltage?
a) φ=cos-1V/VR
b) φ=cos-1V*VR
c) φ=cos-1VR/V
d) φ=tan-1V/VR

Explanation: Form the voltage triangle, we get cosφ= VR/V.
Hence φ=cos-1VR/V.

5 - Question

What is tanϕ for RC circuit?
a) XC/R
b) XL/R
c) R/Z
d) Z/R

Explanation: From the impedance triangle, height gives capacitive reactance and base gives resistance.
tanϕ=XC/R.

6 - Question

What is the resonance condition?
a) When XL>XC
b) When XL<XC
c) When XL=XC
d) When XC=infinity

Explanation: The current is in phase with the voltage when the capacitive reactance is in equal to the inductive reactance. This is known as resonance condition.

7 - Question

What is the frequency in resonance condition?
a) Minimum
b) Maximum
c) Cannot be determined
d) Zero