Assertion $(A):$ A wire bent into an irregular shape with the points $P$ and $Q$ fixed. If a current $I$ passed through the wire, then the area enclosed by the irregular portion of the wire increases.
Reason $(R):$ Opposite currents carrying wires repel each other.
If both Assertion and Reason are true and Reason is correct explanation of Assertion.
If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
If Assertion is true but Reason is false.
If both Assertion and Reason are false.
An arbitrary shaped closed coil is made of a wire of length $L$ and a current $I$ ampere is flowing in it. If the plane of the coil is perpendicular to magnetic field $\mathop B\limits^ \to $, the force on the coil is
The magnetic force between wires as shown in figure is :-
Force on current carrying loop (Radius $= R$ ) in uniform magnetic $(B)$ field which is at an angle $30^{\circ}$ with the normal will be
A semi circular arc of radius $r$ and a straight wire along the diameter, both are carrying same current $i.$ Find out magnetic force per unit length on the small element $P$, which is at the centre of curvature.
Two parallel long wires carry currents $i_1$ and $i_2$ with ${i_1} > {i_2}$. When the currents are in the same direction, the magnetic field midway between the wires is $10\, \mu T$. When the direction of $i_2$ is reversed, it becomes $40 \,\mu T$. the ratio ${i_1}/{i_2}$ is