Question

A current loop `ABCD` is held fixed on the plane of the paper as shown in figure. The arcs `BC( radius = b) and DA ( radius = a)` of the loop are joined by two straight wires `AB and CD` at the origin `O` is 30^(@)`. Another straight thin wire with steady current `I_(1)` flowing out of the plane of the paper is kept at the origin .

Due to the process of the current `I_(1)` at the origin:
A. The force on `AB` and `DC` are zero
B. The forces on `AD` and `BC` are zero
C. The magnitude of the net force on the loop is given by `(mu_(0)II_(1))/(4pi)[2(b-a)+(pi)/(3)(a+b)]`
D. The magnitude of the net force on the loop is given by `(mu_(0)II_(1))/(4pi)[(b-a)/(ab)]`

Answer 1

Correct Answer - 3
The forces on `AD` and `BC` are zero because magnetic field due to a straight wire on `AD` and `BC` is parallel to elementary lenth of the loop.