Question

A circular coil $ABCD$ carrying a current ${}^{\prime }{i}^{\prime }$ is placed in a uniform magnetic field. If the magnetic force on the segment $AB$ is $\vec{F}$, the force on the remaining segment $BCDA$ is

• A. $-\vec{F}$
• B. $3\vec{F}$
• C. $-3\vec{F}$
• D. $\vec{F}$

Answer 1

Answer: (A)

The net magnetic force on a current loop in a uniform magnetic field is always zero.
$\therefore {\vec{F}}_{AB}+{\vec{F}}_{BCDA}=0$
${\vec{F}}_{BCDA}=-{\vec{F}}_{AB}=-\vec{F}$