Network Theory Questions and Answers – Thevenin’s Theorem

This set of Network Theory Multiple Choice Questions & Answers (MCQs) focuses on “Thevenin’s Theorem”.

1. Thevenin’s voltage is equal to the _____________ voltage across the _______________ terminals.
a) short circuit, input
b) short circuit, output
c) open circuit, output
d) open circuit, input
View Answer

Answer: c
Explanation: Thevenin’s voltage is equal to open circuit voltage across output terminals not the short circuit voltage across output terminals.

2. Consider the circuit shown below. The expression of Thevenin’s voltage (VTh) is?
The expression of Thevenin’s voltage (VTh) is V(Z2/(Z1+Z2)) in circuit
a) V(Z1/(Z1+Z2))
b) V(Z2/(Z1+Z2))
c) V(Z1)
d) V(Z2)
View Answer

Answer: b
Explanation: Thevenin’s theorem gives us a method for simplifying a given circuit. The thevenin’s voltage is VTh = V(Z2/(Z1+Z2)).

3. The value of ZTh in the circuit shown below is?
The expression of Thevenin’s voltage (VTh) is V(Z2/(Z1+Z2)) in circuit
a) Z3+(Z1Z2/(Z1+Z2))
b) Z1+(Z3Z2/(Z3+Z2))
c) Z2+(Z1Z3/(Z1+Z3))
d) (Z1Z2/(Z1+Z2))
View Answer

Answer: a
Explanation: The thevenin’s equivalent form of any complex impedance consists of an equivalent voltage source and an equivalent impedance. The thevenin’s impedance is ZTh = Z3+(Z1Z2/(Z1+Z2)).
advertisement
advertisement

4. In the circuit shown below, find the thevenin’s voltage across ‘ab’ terminals.
Find the thevenin’s voltage across ‘ab’ terminals in the circuit
a) 48.5∠40.35⁰
b) 48.5∠-40.35⁰
c) 49.5∠-40.35⁰
d) 49.5∠40.35⁰
View Answer

Answer: d
Explanation: Though the thevenin’s equivalent circuit is not same as its original circuit, the output current and voltage are the same in both cases. The thevenin’s voltage is equal to the voltage across (4+j6)Ω impedance. VTh =50∠0o×(4+j6)/((4+j6)+(3-j4))=49.5∠40.35⁰V.

5. Find the thevenin’s impedance in the circuit shown below.
Find the thevenin’s voltage across ‘ab’ terminals in the circuit
a) 4.83∠-1.13⁰
b) 5.83∠1.13⁰
c) 4.83∠1.13⁰
d) 5.83∠-1.13⁰
View Answer

Answer: a
Explanation: The impedance is equal to the impedance seen into the network across the output terminals. ZTh = (j5-j4)+(3-j4)(4+j6)/(3-j4+4+j6) = 4.83∠-1.13⁰Ω.

6. Determine the Thevenin’s voltage across ‘ab’ terminals in the circuit shown below.
Find the Thevenin’s voltage across ‘ab’ terminals in the circuit shown
a) 41.86∠0⁰
b) 42.86∠0⁰
c) 43.86∠0⁰
d) 44.86∠0⁰
View Answer

Answer: b
Explanation: The voltage across the points a and b is called thevenin’s equivalent voltage. Thevenin’s equivalent voltage Vab=100∠0o×j3/(j3+j4) = 42.86∠0o V.

7. Find the Thevenin’s impedance across ‘ab’ terminals in the circuit shown below.
Find the Thevenin’s voltage across ‘ab’ terminals in the circuit shown
a) j4.71
b) j5.71
c) j6.71
d) j7.71
View Answer

Answer: c
Explanation: The impedance is equal to the impedance seen into the network across the output terminals. Zab=j5 + (j4)(j3)/j7 = j6.71Ω.
advertisement

8. Determine the load current across j5Ω in the circuit shown below.
The expression of Thevenin’s voltage (VTh) is V(Z2/(Z1+Z2)) in circuit
a) 3.66∠90⁰
b) 3.66∠-90⁰
c) 4.66∠90⁰
d) 4.66∠-90⁰
View Answer

Answer: b
Explanation: The load current is the ratio of thevenin’s equivalent voltage and thevenin’s equivalent impedance. The load current IL = (42.86∠0o)/(j6.71+j5) = 3.66∠-90o A.

9. Determine the thevenin’s voltage in the circuit shown below.
The thevenin’s voltage in the circuit is 18∠146.31⁰ in circuit
a) 18∠146.31⁰
b) 18∠-146.31⁰
c) 19∠146.31⁰
d) 19∠-146.31⁰
View Answer

Answer: a
Explanation: The voltage across (-j4) Ω resistor is = (5∠90o)/((2+j2)) (-j4) = 7.07∠-45o V. The voltage across ‘ab’ = -10∠0o+5∠90o-7.07∠-45o=18∠146.31o V.
advertisement

10. Find the Thevenin’s impedance in the following circuit.
The thevenin’s voltage in the circuit is 18∠146.31⁰ in circuit
a) 11.3∠45⁰
b) 12.3∠45⁰
c) 11.3∠-45⁰
d) 12.3∠-45⁰
View Answer

Answer: c
Explanation: The impedance is equal to the impedance seen into the network across the output terminals. Zab = 4 + (2+j6)(-j4)/(2+j2) = 11.3∠-45o Ω.

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.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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 & discussions at Telegram SanfoundryClasses.