This set of Network Theory Multiple Choice Questions & Answers (MCQs) focuses 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

View Answer

Explanation: 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 )

View Answer

Explanation: 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

View Answer

Explanation: 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

View Answer

Explanation: 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

View Answer

Explanation: 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

View Answer

Explanation: 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 in the question 6?

a) di/dt+i=1

b) di/dt+i=2

c) di/dt+i=3

d) di/dt+i=0

View Answer

Explanation: By applying Kirchhoff’s law, we get

Differentiating with respect to t, we get 10 di/dt+i/0.1=0 => di/dt+i=0.

8. The current equation in the circuit shown in the question 6 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

View Answer

Explanation: 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 in the question 6 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

View Answer

Explanation: 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 in the question 6 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

View Answer

Explanation: The expression of voltage across capacitor in the circuit V

_{C}= V(1-e

^{-t/RC}) =20(1-e

^{-t})V.

**Sanfoundry Global Education & Learning Series – Network Theory.**

To practice all areas of Network Theory, __here is complete set of 1000+ Multiple Choice Questions and Answers__.