Question

Two inductors whose self-inductances are of $15\text{mH}$ and $25\text{mH}$ respectively are connected together in parallel aiding. Their mutual inductance is given as $5\text{mH}$. Calculate the total inductance of the parallel combination.

• A. $17.7\text{mH}$
• B. $11.7\text{mH}$
• C. $13.7\text{mH}$
• D. $15.7\text{mH}$

Answer 1

The correct option is B $11.7\text{mH}$

We know that, for a parallel combination of inductors such that their magnetic fields aid each other, net inductance is given by,

$L_{eq}=\frac{L_1{L}_2-M^2}{L_1+L_2-2M}$

$\Rightarrow L_{eq}=\frac{15\times 25-5^2}{15+25-2\times 5}$

$\Rightarrow L_{eq}=11.7\text{mH}$