Question

Two coils of turns N1 and N2 having current I1 and I2 of length L are coupled on same core having radius r1 and r2 find

the expression for mutual inductance between the coils.

​

Answer 1

Explanation:

coil B kept near another coil A has magnetic flux passing through it when kept near coil A. The ratio of magnetic flux through the coil B to the current in the coil A is called as mutual inductance of coil A and coil B.

M

12

=

i

ϕ

2

Let S

1

carries a current i.

Magnetic field inside S

1

will be B=μ

o

N

1

i/l

Flux through each turn of S

2

is ϕ=B×πr

2

2

ϕ=μ

o

N

1

πr

2

2

i/l

Flux through all turns of S

2

is ϕ

B

=ϕN

2

ϕ

B

=μ

o

N

1

πr

2

2

iN

2

/l

M=

i

ϕ

B

=

l

μ

o

N

1

N

2

πr

2

2