A square current carrying loop is suspended in a unifrom magnetic field acting in the palne of the loop. If the force on one arm of the loop is `vec(F)`, the net force on the remaining three arms of the loop is

Options

A. `vecF`
B. `-3vecF`
C. `vec-F`
D. `3vecF`

Answer

C

Explanation

When the coil is freely suspended in a uniform magnetic field, a torque `tau=mIAB sin theta` acts on the coil. The forces `vecF_1 and vecF_2` are equal and opposite and they have the same line of action. They cancel each other. But equal and opposite and they have the same line of action. They cancel each other. But equal and opposite forces `vecF_3 and vecF_4` have different lines of action.`therefore` They form a couple `thereforevecF_4=-vecF_3` Or if the force on one arm is F, the net force acting on the remaining three arms of the loop will be-F(the remaining two will cancel each other).