Question

A square loop of wire is placed in a magnetic field as shown below. If the direction of current flow is clockwise, what is the direction of the net force on the loop?

• A. Up the page
• B. Down the page
• C. To the left
• D. To the right
• E. The net force is zero.

Answer 1

Answer: (E)

The net force is zero.

We can take four sides of square as four separate current carrying wires , if we apply Fleming's left hand rule to find the force on each side , we find that ,forces on top and bottom sides are equal and opposite (cancel each other) and forces on left and right sides are also equal and opposite , therefore net force on loop is zero .

magnetic force on top side $F_t=ILB\sin 90=ILB$ (up the page ) ,

magnetic force on bottom side $F_b=ILB\sin 90=ILB$ (down the page) ,

magnetic force on left side $F_l=ILB\sin 90=ILB$ (to the left of the page ) ,

magnetic force on right side $F_r=ILB\sin 90=ILB$ (to the right of the page )