Question

Two long straight parallel wires carry currents I1 and I2 in the same direction. Find an expression for the force per unit length between them. Depict the pattern of magnetic field lines. Use the expression to define S.I unit of current.​

Answer 1

Answer:

here!

Explanation:

Magnetic field due to wire a on b =2πdμ0​Ia​​

Force on a current carrying wire placed in magnetic field=I(l×B)

Hence force on b is Fba​=Ib​l2πdμ0​Ia​​

The direction of force experienced by the wire 'a' is toward the wire 'b' as shown.

Similarly the direction of force experienced by the wire 'b' is toward the wire Thus, the force is attractive.

If two long wires are placed in a vacuum at a separation of 1 m, one Ampere would be defined as the current in each wire that would produce a force  per unit length of wire.