Coupled Circuits MCQs

Practice Coupled Circuits MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 1

Network TheoryCoupled Circuits

Two identical uncoupled inductors of 4 H each are connected in series. Their equivalent inductance is?

A2 H
B4 H
C8 H
D16 H

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Correct Answer: C. 8 H

Explanation: For uncoupled inductors in series, inductances add: Leq=4+4=8 H.

Reference: Standard network theory: uncoupled inductors

Question 2

Network TheoryCoupled Circuits

Two magnetically coupled coils have L1=4 H, L2=9 H, and coupling coefficient k=0.5. Their mutual inductance M is?

A1.5 H
B3 H
C6 H
D18 H

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Correct Answer: B. 3 H

Explanation: M=k sqrt(L1L2)=0.5×sqrt(4×9)=0.5×6=3 H.

Reference: Standard network theory: mutual inductance numerical

Question 3

Network TheoryCoupled Circuits

The coefficient of coupling k between two passive coupled coils normally lies in the range?

A0 to 1
B1 to 10
C-10 to 10 only
DGreater than 1

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Correct Answer: A. 0 to 1

Explanation: The magnitude of coupling coefficient is bounded by 0<=k<=1, where k=1 represents ideal complete coupling.

Reference: Standard network theory: coefficient of coupling

Question 4

Network TheoryCoupled Circuits

For two coupled inductors connected in series aiding, the equivalent inductance is?

AL1+L2-2M
BL1+L2+2M
CL1L2/M
DM-L1-L2

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Correct Answer: B. L1+L2+2M

Explanation: With series-aiding polarity, mutual flux reinforces self flux, giving Leq=L1+L2+2M.

Reference: Standard network theory: series-aiding coupled coils

Question 5

Network TheoryCoupled Circuits

Two coupled coils have L1=2 H, L2=3 H and M=1 H. If connected in series opposing, their equivalent inductance is?

A1 H
B3 H
C5 H
D7 H

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Correct Answer: B. 3 H

Explanation: For series-opposing connection, Leq=L1+L2-2M=2+3-2=3 H.

Reference: Standard network theory: series-opposing coupled coils

Question 6

Network TheoryCoupled Circuits

An ideal transformer has turns ratio N1/N2=4. A 100 ohm load connected to the secondary is reflected to the primary as?

A6.25 ohm
B25 ohm
C400 ohm
D1600 ohm

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Correct Answer: D. 1600 ohm

Explanation: The reflected impedance is Zp=(N1/N2)^2 ZL=4^2×100=1600 ohm.

Reference: Standard network theory: transformer impedance reflection

Question 7

Network TheoryCoupled Circuits

An ideal transformer has N1/N2=5 and primary voltage 250 V RMS. The secondary voltage magnitude is?

A10 V
B50 V
C250 V
D1250 V

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Correct Answer: B. 50 V

Explanation: For an ideal transformer, V1/V2=N1/N2=5, so V2=250/5=50 V.

Reference: Standard network theory: ideal transformer voltage ratio

Question 8

Network TheoryCoupled Circuits

For an ideal transformer with N1/N2=5, if the secondary current is 10 A, the primary current magnitude is?

A2 A
B5 A
C10 A
D50 A

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Correct Answer: A. 2 A

Explanation: For an ideal transformer, I1/I2=N2/N1=1/5, hence I1=10/5=2 A.

Reference: Standard network theory: ideal transformer current ratio

Question 9

Network TheoryCoupled Circuits

If the dot convention shows current entering the dotted terminal of coil 1 and the mutually induced voltage of coil 2 is referenced positive at its dotted terminal, the mutual-voltage term is taken as?

A+M di1/dt
B-M di1/dt
CZero for all coupling
DM/i1

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Correct Answer: A. +M di1/dt

Explanation: With the stated dot-reference convention, current entering a dotted terminal induces a voltage positive at the dotted terminal of the other coil, giving a positive mutual term.

Reference: Standard network theory: dot convention

Question 10

Network TheoryCoupled Circuits

Two coils have mutual inductance M=0.2 H. If current in coil 1 changes at 5 A/s, the magnitude of the mutually induced voltage in coil 2 is?

A0.04 V
B0.2 V
C1 V
D25 V

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Correct Answer: C. 1 V

Explanation: The magnitude is |v2|=M|di1/dt|=0.2×5=1 V.

Reference: Standard network theory: mutual induced voltage numerical

Question 11

Network TheoryCoupled Circuits

For two coupled inductors, the maximum physically possible mutual inductance magnitude is?

AL1+L2
Bsqrt(L1L2)
CL1L2
D|L1-L2|

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Correct Answer: B. sqrt(L1L2)

Explanation: Since |k|<=1 and M=k sqrt(L1L2), the maximum magnitude of M is sqrt(L1L2).

Reference: Standard network theory: mutual inductance limit