$A$ circular current loop of radius $a$ is placed in a radial magnetic field $B$ as shown in the figure. The net force acting on the loop is

The circuit in the figure consists of wires at the top and bottom and identical springs as the left and right sides. The wire at the bottom has a mass of $10 \, g$ and is $5 \, cm$ long. The wire is hanging as shown in the figure. The springs stretch $0.5 \, cm$ under the weight of the wire and the circuit has a total resistance of $12 \, \Omega$. When the lower wire is subjected to a static magnetic field,the springs stretch an additional $0.3 \, cm$. The magnetic field is

$A, B$ and $C$ are parallel conductors of equal length carrying currents $I, I$ and $2I$ respectively. The distance between $A$ and $B$ is $x$. The distance between $B$ and $C$ is also $x$. If $F_1$ is the force exerted by $B$ on $A$ and $F_2$ is the force exerted by $C$ on $B$,choose the correct answer.

$A$ power line lies along the east-west direction and carries a current of $10\, A$. The force per metre due to the earth's magnetic field of ${10^{ - 4}}\, T$ is

$A$ square loop,carrying a steady current $I$,is placed in a horizontal plane near a long straight conductor carrying a steady current $I_1$ at a distance $d$ from the conductor as shown in the figure. The loop will experience:

$A$ conducting circular loop of radius $r$ carries a constant current $i$. It is placed in a uniform magnetic field $B$,such that $B$ is perpendicular to the plane of the loop. The net magnetic force acting on the loop is