Question

Obtain the formula for the force of attraction between two parallal wires carrying currents in the same direction.

Answer 1

Let the two wires by wire 1 and wire 2 with I1 and I2 current respectively.

Magnetic field at wire 2 from current in wire 1;

B = μ0 * I1 / 2 * pi * r

The force on the length delta L of wire 2,

F = I2 * delta L * B

Force per unit length in terms of the currents:

F/Delta L = μ0 I1 * I2/ 2 * pi * r