Question

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

• A. $13H$
• B. $17H$
• C. $28H$
• D. $6H$

Answer 1

The correct option is D $6H$

Given,
$L_1+L_2=13$ ....(i)
and, $L_1-L_2=5$ ....(ii)

On solving equation (i) and (ii),
$L_1=9H$
$L_2=4H$

Mutual inductance between two coils is given by,
$M_{max}=K\sqrt{L_1{L}_2}$

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