Question

The sum and the difference of self-inductance of two coils are 13 H and 5 H respectively. The maximum mutual inductances of the two coils is,

• A. 13 H
• B. 5 H
• C. 28 H
• D. 6 H

Answer 1

The correct option is D 6 H

$L_1+L_2=13$

$L_1-L_2=5$

$L_1=9H$

$L_2=4H$

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

$M_{\text{max}}=1\sqrt{9\times 4}=6H$