A large metal sheet carries an electric current along its surface. Current per unit length is $\lambda$.

Magnetic field induction near the metal sheet is

Two straight infinitely long current-carrying wires are kept along $z$-axis at the coordinates $\left(0, a, 0\right)$ and $\left(0, -a, 0\right)$ respectively as shown in the figure. The current in each of the wire is equal and along negative $z$-axis (into the plane of the paper). The variation of the magnetic field on the $x$-axis will be approximately,

A wires $PQRS$ carrying a current $I$ runs along three edges of a cube of side $l$ as shown. There exists a uniform magnetic field of magnitude $B$ along one of the sides of the cube. The magnitude of the force acting on the wire is

The magnetic field at the centre of square of side $a$ is

A particle of charge $-q$ and mass $m$ enters a uniform magnetic field $B$ (perpendicular to paper inwards) at $P$ with a speed $v_0$ at an angle $\alpha$ and leaves the field at $Q$ with speed $v$ at angle $\beta$ as shown in the figure. Then,