Two long and parallel wires are at a distance of $0.1\, m$ and a current of $5\, A$ is flowing in each of these wires. The force per unit length due to these wires will be
$5 \times {10^{ - 5}}\,N/m$
$5 \times {10^{ - 3}}\,N/m$
$2.5 \times {10^{ - 5}}\,N/m$
$2.5 \times {10^{ - 4}}\,N/m$
Derive an expression for the force per unit length between two infinitely long straight parallel current carrying wires. Hence, define one ampere $( \mathrm{A} )$.
A circular current loop of radius a is placed in a radial field $B$ as shown. The net force acting on the loop is
A rectangular loop of wire, supporting a mass $m$, hangs with one end in a uniform magnetic field $\vec B$ pointing into the plane of the paper. $A$ clockwise current is set up such that $i> mg/Ba,$ where $a$ is the width of the loop. Then
A conducting circular loop of radius $r$ carries a constant current $i$. It is placed in uniform magnetic field $B$, such that $B$ is perpendicular to the plane of the loop. The net magnetic force acting on the loop is
A metallic rod of mass per unit length $0.5\; kg\; m^{-1}$ is lying horizontally on a smooth inclined plane which makes an angle of $30^o$ with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction $0.25\; T$ is acting on it in the vertical direction. The current flowing in the rod to keep it stationary is.....$A$