Question

Two coils of self-inductance 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils are

• A. 16 mH
• B. 10 mH
• C. 6 mH
• D. 4 mH

Answer 1

Answer: (D)

4 mH

Answer 2

Mutual inductance between coils is

$M = k\sqrt{L_{1} + L_{2}}$

$= 1\sqrt{2 \times 10^{- 3} \times 8 \times 10^{- 3}}$ ($\because k = 1$)

$= 4 \times 10^{- 3}H = 4mH$