Question

.
Two long parallel conducting wires carry current
I in same direction, placed at distance b. Force per
unit length of wire is :-​

Answer 1

Given:

The current flowing in the wire is I.

The length of wire L.

The distance between them is b.

To find:

The force per unit length of wire.

Solution:

The magnetic field at due to one  wire is

B'=μI'/2πb

Now force acting on the wire two due to first one

F=I"L'B'=μI'I"L'/2πb

Now the force per unit length is

F'=F/L'

Put the above value

F'=μI'I"/2πb

So the force per unit length of wire is μI'I"/2πb