250+ TOP MCQs on DC Response of an R-C Circuit and Answers

Network Theory Multiple Choice Questions on “DC Response of an R-C Circuit”.

1. The current in the R-L circuit at a time t = 0⁺ is?
A. V/R
B. R/V
C. V
D. R

Answer: A
Clarification: The capacitor never allows sudden changes in voltage, it will act as a short circuit at t = 0⁺. So the current in the circuit at t = 0⁺ is V/R.

2. The expression of current in R-C circuit is?
A. i=(V/R)exp⁡(t/RC.
B. i=(V/R)exp⁡(-t/RC.
C. i=(V/R)-exp(⁡t/RC.
D. i=(V/R)-exp⁡(-t/RC.

Answer: B
Clarification: The particular solution of the current equation is zero. So the expression of current in R-C circuit is i=(V/R)exp⁡(-t/RC..

3. In an R-C circuit, when the switch is closed, the response ____________
A. do not vary with time
B. decays with time
C. rises with time
D. first increases and then decreases

Answer: B
Clarification: In a R-C circuit, when the switch is closed, the response decays with time that is the response V/R decreases with increase in time.

4. The time constant of an R-C circuit is?
A. RC
B. R/C
C. R
D. C

Answer: A
Clarification: The time constant of an R-C circuit is RC and it is denoted by τ and the value of τ in dc response of R-C circuit is RC sec.

5. After how many time constants, the transient part reaches more than 99 percent of its final value?
A. 2
B. 3
C. 4
D. 5

Answer: D
Clarification: After five time constants, the transient part of the response reaches more than 99 percent of its final value.

6.A series R-C circuit consists of resistor of 10 and capacitor of 0.1F as shown in the figure. A constant voltage of 20V is applied to the circuit at t = 0. What is the current in the circuit at t = 0?

A. 1
B. 2
C. 3
D. 4

Answer: B
Clarification: At t = 0, switch S is closed. Since the capacitor does not allow sudden changes in voltage, the current in the circuit is i = V/R = 20/10 = 2A. At t = 0, i = 2A.

7. The expression of current obtained from the circuit in terms of differentiation from the circuit shown below?

A. di/dt+i=1
B. di/dt+i=2
C. di/dt+i=3
D. di/dt+i=0

8. The current equation in the circuit shown below is?

A. i=2(e^-2t)A
B. i=2(e^2t)A
C. i=2(-e^-2t)A
D. i=2(-e^2t)A

Answer: A
Clarification: At t = 0, switch S is closed. Since the capacitor does not allow sudden changes in voltage, the current in the circuit is i = V/R = 20/10 = 2A. At t = 0, i = 2A. The current equation is i=2(e^-2t)A.

9. The expression of voltage across resistor in the circuit shown below is?

A. V_R = 20(e^t)V
B. V_R = 20(-e^-t)V
C. V_R = 20(-e^t)V
D. V_R = 20(e^-t)V

Answer: D
Clarification: The expression of voltage across resistor in the circuit is V_R = iR =(2(e^-t))×10=20(e^-t)V.

10. Determine the voltage across the capacitor in the circuit shown below is?

A. V_C = 60(1-e^-t)V
B. V_C = 60(1+e^t)V
C. V_C = 60(1-e^t)V
D. V_C = 60(1+e^-t)V

Answer: A
Clarification: The expression of voltage across capacitor in the circuit V_C = V(1-e^-t/RC) = 20(1-e^-t)V.