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