Basic Electrical Engineering Questions and Answers – Transients in CR Networks

«
»

This set of Basic Electrical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Transients in CR Networks”.

1. A CR network is one which consists of _________
a) A capacitor and resistor connected in parallel
b) A capacitor and resistor connected in series
c) A network consisting of a capacitor only
d) A network consisting of a resistor only
View Answer

Answer: b
Explanation: A CR network is one which consists of a capacitor connected in series with a resistor. The capacitor discharges or charges through the resistor.
advertisement

2. At DC, capacitor acts as _________
a) Open circuit
b) Short circuit
c) Resistor
d) Inductor
View Answer

Answer: a
Explanation: Capacitive Reactance XC = 1/(2πfC)
For DC, f=0 so, XC becomes infinite. Hence for dc, the capacitor acts as an open circuit.

3. In an RC series circuit, when the switch is closed and the circuit is complete, what is the response?
a) Response does not vary with time
b) Decays with time
c) Increases with time
d) First increases, then decrease
View Answer

Answer: b
Explanation: In an RC series circuit, the response decays with time because according to the equation, there is an exponential decrease in the response.
Sanfoundry Certification Contest of the Month is Live. 100+ Subjects. Participate Now!
advertisement
advertisement

4. If the switch is closed at t=0, what is the current in the circuit?
Find the current in the circuit if the switch is closed at t=0
a) 0A
b) 10A
c) 20A
d) Infinity
View Answer

Answer: b
Explanation: As soon as the switch is closed at t=0, the capacitor acts as a short circuit. The current in the circuit is:
I=V/R = 100/10 = 10A.

5. Calculate the voltage across the capacitor at t=0.
Find the voltage across capacitor at t=0 if capacitor has no voltage across it
a) 0V
b) 10V
c) 20V
d) Infinity
View Answer

Answer: a
Explanation: When the switch is closed at t=0, the capacitor has no voltage across it since it has not been charged. The capacitor acts as a short circuit and the voltage across it is zero.
advertisement

6. Calculate di(0)/dt if the switch is closed at t=0.
Find the value of di(0)/dt if the switch is closed at t=0
a) -9.9A/s
b) -10A/s
c) 0A/s
d) -0.1A/s
View Answer

Answer: d
Explanation: Applying KVL to the given circuit, we get:
i=i0e-t/RC = (100/10)e-t/100
i=10 e-t/100
di/dt = -(10/100) e-t/100
di(0)/dt=-0.1A/s.

7. Calculate d2i(0)/dt2 from the given circuit.
Find the value of d2i(0)/dt2 by applying KVL to the given circuit
a) 10-6A/s2
b) 10-3A/s2
c) 106A/s2
d) 103A/s2
View Answer

Answer: b
Explanation: Applying KVL to the given circuit, we get:
100+10i(0)+1/10*integral(i(0)dt)=0
Differentiating once, we get:
10di(0)/dt+1/10*i.
Differentiating once again, we get:
10d2i(0)/dt2+10di(0)/dt=0.
Substituting the values of di/dt from the previous explanation, we get d2i(0)/dt2=10-3A/s2.
advertisement

8. The current equation for the given circuit is?
Find the current equation for given circuit by applying Laplace transform
a) i=10e(-0.01)t A
b) i=10e(0.01)t A
c) i=10e(-0.001)t A
d) i=100e(-0.01)t A
View Answer

Answer: a
Explanation: The KVL equation is:
100+10i(0)+1/10*integral(i(0)dt)=0
On applying Laplace transform to this equation, we get:
100/s=I(s)/10s+10I(s)
Solving the equation, we get:
i=10e(-0.01)t A.

9. The expression for the current in an RC circuit is?
a) i=(V/R)et/RC
b) i=(V/R)e-t/RC
c) i=(V/R)(1-e-t/RC)
d) i=(V/R) (1-et/RC)
View Answer

Answer: b
Explanation: Applying KVL to the given circuit, we get:
i=i0e-t/RC = (100/10)e-t/100
i=10 e-t/100.
advertisement

10. What is the voltage in the resistor as soon as the switch is closed at t=0.
Find the voltage in the resistor as soon as the switch is closed at t=0
a) 0V
b) Infinity
c) 220V
d) Insufficient information provided
View Answer

Answer: c
Explanation: As soon as the switch is closed at t=0, there is no charge in the capacitor, hence the voltage across the capacitor is zero and all the 220V voltage is the voltage across the resistor.

Sanfoundry Global Education & Learning Series – Basic Electrical Engineering.

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

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

Subscribe to his free Masterclasses at Youtube & technical discussions at Telegram SanfoundryClasses.