A conducting circular loop of radiius `r` carries a constant current `i`. It is placed in a uniform magnetic field `vec(B)_(0)` such that `vec(B)_(0)` is perpendicular to the plane of the loop . The magnetic force acting on the loop is

Options

A. `ir B _(0)`
B. `2pir B _(0)`
C. zero
D. `pi irB _(0)`

Answer

C

Explanation

The magnetic field perpendicular to the plane of the paper. Let us consider diametrically opposite elements on the loop. Applying Fleming.s left-hand rule on element AB, the is two direction of force will be leftwards and the magnitude will be
`dF = I dl B sin 90^(@) = I dlB`

On element CD, the direction of force will be rightwards on the plane of magnitude will be dF = IdlB. the paper and the
Hence, the net force on the loopp due to current elements will be zero, which implies that the total force on the loop will be zero.