Electric Circuits Questions and Answers – Thevenin and Norton Equivalents, More on Deriving a Thevenin Equivalent

This set of Electric Circuits Questions and Answers for Experienced people focuses on “Thevenin and Norton Equivalents, More on Deriving a Thevenin Equivalent”.

1. Find the voltage across 24Ω resistor by using Thevenin’s theorem.
The voltage across 24Ω resistor by using Thevenin’s theorem is 8V
a) 8V
b) 9V
c) 1V
d) 6V
View Answer

Answer: a
Explanation: 1. Remove 24Ω resistor and calculate the voltage across the open circuit.
2. Calculate the thevenin’s resistance and by using it, the thevenin’s current.
3. V24Ω=I*R (can also verify by using Nodal analysis).

2. Calculate Thevenin’s voltage for the network shown below where the voltage source is 4V.
The Thevenin’s voltage for the network shown is 5V where the voltage source is 4V
a) 6V
b) 4.71V
c) 5V
d) 1V
View Answer

Answer: c
Explanation: In the circuit given, thevenin’s voltage is nothing but the open circuit voltage which is Vx. Applying KVL, it is obtained.

3. Find the Thevenin’s resistance for the network given.
The Thevenin’s resistance for the network given is 6.75Ω
a) 6.75Ω
b) 5.85Ω
c) 4.79Ω
d) 1.675Ω
View Answer

Answer: a
Explanation: Remove all the voltage/current sources and calculate the equivalent resistance.
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4. Find the current through (5+j4) Ω resistor.
The current through (5+j4) Ω resistor is 0.9-j0.2 A
a) 0.9-j0.2 A
b) 0.78-j0.1 A
c) 2.7-j0.5 A
d) 1A
View Answer

Answer: a
Explanation: 1. Remove the 5+j4 Ω branch and calculate thevenin’s voltage.
(V= v across 6Ω resistor- v across 8Ω resistor)
2. Calculate Zth. (10//6 and 8//8)
3. Current= (Vth/ (Zth+Z).

5. The voltage across 6Ω resistor is __________
The voltage across 6Ω resistor is 8.5V by using short circuit current & resistance
a) 7.5V
b) 6.78V
c) 20V
d) 8.5V
View Answer

Answer: d
Explanation: Remove the resistor across which voltage is to be calculated and short circuit it. By using short circuit current and resistance calculate the current across 6Ω resistor and thereby voltage. (In this 10Ω resistor is also short-circuited since 10//0).
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6. Find the Norton’s current for the circuit given below.
Find the Norton’s current for the circuit given below
a) 5A
b) 3.33A
c) 4A
d) 1.66A
View Answer

Answer: c
Explanation: IN= (20/10) + (10/5).

7. Calculate IN for the given network.
The IN for the given network is 0A using nodal analysis Vx
a) 0A
b) 1A
c) 4.37A
d) 0.37A
View Answer

Answer: a
Explanation: Using nodal analysis Vx is calculated. IN =Vx/4.
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8. Calculate RTh for the network given.
The RTh for the network given is 7Ω for in series with 3Ω resistor
a) 8Ω
b) 7Ω
c) 2Ω
d) 1Ω
View Answer

Answer: b
Explanation: 5//20 and then in series with 3Ω resistor.

9. Thevenin’s equivalent circuit consists of a ____________
a) Voltage source in series with a resistor
b) Current source in parallel with a resistor
c) Voltage source in parallel with a resistor
d) Current source in series with a resistor
View Answer

Answer: a
Explanation: Thevenin’s equivalent circuit contains a Voltage source in series with a resistor.
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10. Norton’s equivalent circuit consists of a _____________
a) Voltage source in series with a resistor
b) Current source in parallel with a resistor
c) Both voltage and current sources
d) Current source in series with a resistor
View Answer

Answer: b
Explanation: Norton’s equivalent circuit consists of a Current source in parallel with a resistor.

11. Thevenin’s voltage is equal to ____________
a) Short circuit voltage
b) Open circuit current
c) Open circuit voltage
d) Short circuit current
View Answer

Answer: c
Explanation: Thevenin’s voltage is equal to open circuit voltage.

12. Norton’s current is equal to ____________
a) Short circuit voltage
b) Open circuit current
c) Open circuit voltage
d) Short circuit current
View Answer

Answer: d
Explanation: Norton’s current is equal to Short circuit current.

13. Thevenin’s resistance RTh = ___________
a) VTh/ISC
b) VSC/ITh
c) VTh/ITh
d) VSC /ISC
View Answer

Answer: a
Explanation: Thevenin’s resistance is defined as the ratio of open circuit voltage to the short circuit current across the terminals of the original circuit.

14. What is the expression forthe thevenin’s current if there is an external resistance in series with the RTh?
a) VTh/ITh
b) VTh/ (RTh-R)
c) VTh/ (RTh+R)
d) VTh/RTh
View Answer

Answer: c
Explanation: ITh= VTh/ (RTh+R).

15. One can find the thevenin’s resistance simply by removing all voltage/current sources and calculating equivalent resistance.
a) False
b) True
View Answer

Answer: b
Explanation: Yes. One can find the thevenin’s resistance simply by removing all voltage/current sources and calculating equivalent resistance.

Sanfoundry Global Education & Learning Series – Electric Circuits.

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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.

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