Question

Two 2 H inductance coils are connected in series and are also magnetically coupled to each other. The coefficient of coupling being 0.1. The total inductance of the combination can be

• A. 0.4 H
• B. 3.2 H
• C. 4.0 H
• D. 4.4 H

Answer 1

The correct option is D 4.4 H

$L=L_1+L_2\pm 2M$
$=L_1+L_2\pm 2k\sqrt{L_1{L}_2}$
$L=2+2\pm 2\left(0.1\right)\sqrt{2\times 2}=4\pm 0.4$
$L=3.6H$ and $4.4H$