Question

A circular coil PQRSP is placed in a uniform magnetic field. When a current flows through the coil, the force on the segment PQ is F. The force on the remaining segment QRSP is

• A. 3F
• B. -3F
• C. F
• D. -F

Answer 1

Answer: (D)

A circular coil $PQRSP$ is placed in a uniform magnetic field. When a current flows through the coil, the force on segment $PQ$ is $\mathbf{F}$ then the force on the remaining segment $QRSP$ is $-\mathbf{F}$ . Aliter $\because$ $F_{\mathrm{close}loop}=0$ ${\mathbf{F}}_{PQ}+{\mathbf{F}}_{QRSP}=0$ ${\mathbf{F}}_{QRSP}=-\mathbf{F}$