Three long,straight parallel wires carrying current are arranged as shown in the figure. The force experienced by a $25\, cm$ length of wire $C$ is

$ABCD$ is a rectangular loop made of uniform wire. If $AD = BC = 2 \text{ cm}$,what is the magnetic force per unit length acting on wire $DC$ due to wire $AB$ if the ammeter reads $20 \text{ A}$? (The lengths of $AB$ and $DC$ are large in comparison with the other two sides).

$A$ thin uniform rod with negligible mass and length $l$ is attached to the floor by a frictionless hinge at point $P$. $A$ horizontal spring with force constant $k$ connects the other end to a wall. The rod is in a uniform magnetic field $B$ directed into the plane of the paper. What is the extension in the spring in equilibrium when a current $i$ is passed through the rod in the direction shown? Assume the spring is initially at its natural length.

$A$ straight horizontal conducting rod of length $0.45\; m$ and mass $60\; g$ is suspended by two vertical wires at its ends. $A$ current of $5.0\; A$ is set up in the rod through the wires.
$(a)$ What magnetic field should be set up normal to the conductor in order that the tension in the wires is zero?
$(b)$ What will be the total tension in the wires if the direction of current is reversed keeping the magnetic field same as before? (Ignore the mass of the wires.) $g = 9.8\; m s^{-2}.$

Two parallel,long wires are kept $0.20 \, m$ apart in a vacuum,each carrying a current of $x \, A$ in the same direction. If the force of attraction per meter of each wire is $2 \times 10^{-6} \, N$,then the value of $x$ is approximately:

$A$ wire is bent in the form of an equilateral triangle of side $100 \,cm$ and carries a current of $2 \,A$. It is placed in a magnetic field of induction $2.0 \,T$ directed perpendicular into the plane of paper. The direction and magnitude of magnetic force acting on each side of the triangle will be