Question

The coefficient of self induction of two inductor
are 20 mH and 40 mH respectively. If the coils a
connected in series so as to support each other and
the resultant inductance is 80 mH then the value of
mutual inductance between the coils will be
(1) 5 mH
(3) 20 mH
(2) 10 mH
(4) 40 mH​

Answer 1

Answer -

M = 10 mH

● Explaination -

# Given -

L1 = 20 mH

L2 = 40 mH

Le = 80 mH

# Solution -

Equivalent inductance of two coils (same direction) in series is -

Le = L1 + L2 + 2M

80 = 20 + 40 + 2M

2M = 80 - 60

M = 20 / 2

M = 10 mH