Question

Two coils of self inductances $2mH$ 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. $10mH$
• B. $16mH$
• C. $4mH$
• D. $6mH$

Answer 1

The correct option is C

$4mH$

Step 1: Given data

Two coils having self-inductance,

$\begin{array}{rcl}{L}_1& =& 2mH\\ L_2& =& 8mH\end{array}$

Step 2: Calculating mutual inductance.

The mutual inductance between the coils is given by,

$H=\sqrt{L_1{L}_2}$, where $"H"$ is the mutual inductance between the coils.

So,

$\begin{array}{rcl}H& =& \sqrt{L_1{L}_2}\\ & =& \sqrt{2\times 8}\\ & =& \sqrt{16}\\ & =& 4mH\end{array}$

Hence, option (C) is correct.