# Basic Electrical Engineering Questions and Answers – Alternating Current in a Capacitive Circuit

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This set of Basic Electrical Engineering Problems focuses on “Alternating Current in a Capacitive Circuit”.

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

Explanation: At resonance condition, the frequency is maximum since the inductive reactance is equal to the capacitive reactance. XL=XC.

Sanfoundry Global Education & Learning Series – Basic Electrical Engineering.

To practice all areas of Basic Electrical Engineering Problems, here is complete set of 1000+ Multiple Choice Questions and Answers.