Question

In the circuit given below, the equivalent inductance is ____________

(a) L1 + L2 – 2M

(b) L1 + L2 + 2M

(c) L1 + L2 – M

(d) L1 + L2

The question was posed to me in an interview for internship.

Asked question is from Series-Series Connection of Two Port Network topic in section Two-Port Networks of Network Theory

Answer 1

The correct option is (a) L1 + L2 – 2M

Easiest explanation: Since, in one inductor current is leaving to dot and in other inductor current is entering to dot.

 So, LEQ = L1 + L2 – 2M.