Question

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

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

Answer 1

Answer: (D)

Mutual inductance between coils is
$\text{M}=\text{K}\sqrt{{\text{L}}_1{\text{L}}_2}$
or, $\text{M}=1\sqrt{2\times 10^{-3}\times 8\times 10^{-3}}$ $\left(\because \text{K}=1\right)$
$=4\times 10^{-3}=4\text{ mH}$