Question

The mutual inductance between two coupled coils is $25mH$. If the turn in one coil is doubled and that in the other is halved, then the mutual inductance will become

• A. $12.5mH$
• B. $25mH$
• C. $50mH$
• D. $100mH$

Answer 1

The correct option is B $25mH$

For ideal case,

$M=\sqrt{L_1{L}_2}$

$\because L\propto N^2$

$L_1=4N^2$ and $L_2=\frac{1}{4}{N}^2$
$\because$ Mutual inductance remains unchanged.