All the flux of coil 1 can never link with coil 2. Loss occurs practically due to which coupling coefficient cannot be equal to 1.

4. Mutual inductance between two coupled coils depends on?

A. Amount of flux linkage
B. Rate of change of flux linkage
C. Rate of change of current
D. Flux density

Answer: B

Faraday’s law of induction states that the magnitude of the induced EMF is the product of the number of turns of the coil and the rate of change of flux linkage in it. Hence, the mutual inductance depends on the rate of change of flux linkage.

5. Which, among the following, is the correct formula to find the coupling coefficient?

A. k = M/√(L1L2)
B. k = M/√(L12)
C. k = M/√(L22)
D. k = M/(L1L2)

Answer: A

The correct formula for the coupling coefficient is k = M/√(L1L2). Where L1 and L2 are the inductance values of the first and second coil respectively and M is the mutual inductance.

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6. What happens to the coupling coefficient when the flux linkage of coil 1 and coil 2 increases?

A. Increases
B. Decreases
C. Remains the same
D. Becomes zero

Answer: A

When the flux linkage of coil 1 and coil 2 increases, its mutual inductance increases. The coupling coefficient is directly proportional to the mutual inductance hence as mutual inductance increases, the coupling coefficient increases.

7. What is the SI unit of the coupling coefficient?

A. H
B. H − 1
C. No unit
D. H2

Answer: C

The expression to find mutual inductance is

k = M/√(L1L2) = H/√(H × H) = 1.

Therefore it does not have any unit.

8. Find the coupling coefficient if the Mutual inductance is 20H, the inductance of coil 1 is 2H and the inductance of coil 2 is 8H.

A. 5
B. 20
C. 2
D. 8

Answer: A

we know that:

k = M/√(L1L2)

Substituting the values from the question, we get k = 5.

9. Find the value of x if the Mutual inductance is x H, the inductance of coil 1 is 2H and the inductance of coil 2 is 8H. The coupling coefficient is 5.

A. 10H
B. 20H
C. 16H
D. 15H

Answer: B

we know that:

k = M/√(L1L2)

Substituting the values from the question, we get M = 20H.

10. Find the value of x if the Mutual inductance is 20H, the inductance of coil 1 is xH and the inductance of coil 2 is 8H. The coupling coefficient is 5.

A. 2H
B. 4H
C. 6H
D. 8H

Answer: A

we know that:

k = M/√(L1L2)

Substituting the values from the question, we get L1 = 2H.