Two parallel wires of equal lengths are separated by a distance of $3 \ m$ from each other. The currents flowing through the $1^{\text{st}}$ and $2^{\text{nd}}$ wires are $3 \ A$ and $4.5 \ A$ respectively in opposite directions. Find the resultant magnetic field at the midpoint between the wires $(\mu_0 = \text{permeability of free space})$.

$A$ negative charge is moving towards the observer. What will be the direction of the magnetic field produced by it,as seen by the observer?

State the Biot-Savart law.

To produce a uniform magnetic field directed parallel to a diameter of a cylindrical region,one can use the saddle coils illustrated in the figure. The loops are wrapped over a somewhat flattened tube. Assume the straight sections of wire are very long. The end view of the tube shows how the windings are applied. The overall current distribution is the superposition of two overlapping circular cylinders of uniformly distributed current,one toward you and one away from you. The current density $J$ is the same for each cylinder. The position of the axis of one cylinder is described by a position vector $\vec{a}$ relative to the other cylinder. The magnetic field inside the hollow tube is:

If the current flowing through the shell of the previous objective is equal to $i$,then the energy density at a point at a distance $2R$ from the axis of the shell varies according to which graph?

$PQ$ and $RS$ are long parallel conductors separated by a certain distance. $M$ is the mid-point between them. The net magnetic field at $M$ is $B$. Now,the current $2\,A$ is switched off. The field at $M$ now becomes