(a) Two straight long parallel conductors carry currents `I_(1)` and `I_(2)` in the same direction. Deduce the expression for the firce per unit length between them.
Depict the pattern of magnetic field lines around them.
(b) A rectangular current carrying loop EFGH is kept in a uniform magnetic field as shown in the figure.
(i) What is the direction of the magnetic moment of the current loop ?
(ii) What is the torque acting on the loop (A) maximum, (B) zero ?

Explanation

(b) (i) Magnetic moment will be out of the plane from the surface HEFG.
(ii) Torque `=vec(M)xxvec(B)`
(A) Torque is maximum when `vec(M)||vec(B)` i.e., when it gets rotated by `90^(@)`.
(B) Torque is minimum when `vec(M)` and `vec(B)` are at `270^(@)` to each other.