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 below?
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 below is?
a) i=2(e-2t)A
b) i=2(e2t)A
c) i=2(-e-2t)A
d) i=2(-e2t)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 below is?
a) VR = 20(et)V
b) VR = 20(-e-t)V
c) VR = 20(-et)V
d) VR = 20(e-t)V
View Answer
Explanation: The expression of voltage across resistor in the circuit is VR = iR =(2(e-t))×10=20(e-t)V.
10. Determine the voltage across the capacitor in the circuit shown below is?
a) VC = 60(1-e-t)V
b) VC = 60(1+et)V
c) VC = 60(1-et)V
d) VC = 60(1+e-t)V
View Answer
Explanation: The expression of voltage across capacitor in the circuit VC = V(1-e-t/RC) = 20(1-e-t)V.
Sanfoundry Global Education & Learning Series – Network Theory.
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