What will happen if two thin, long parallel wires separated by a distance "d" carry current "i" in the same direction?

1.	attract each other with a force per unit length of ${\mu }_0{i}^2/\left(2{\mathrm{\pi d}}^2\right)$
2.	repel each other with a force per unit length of ${\mu }_0{i}^2/\left(2{\mathrm{\pi d}}^2\right)$
3.	attract each other with a force per unit length of ${\mu }_0{i}^2/\left(2\mathrm{\pi d}\right)$
4.	repel each other with a force per unit length of ${\mu }_0{i}^2/\left(2\mathrm{\pi d}\right)$

A long straight wire of radius 'a' carries a steady current I. The current is uniformly distributed over its cross-section. The ratio of the magnetic fields B and B' at radial distances a/2 and 2a respectively, from the axis of the wire, is:

A current loop consists of two identical semicircular parts each of radius \(R\), one lying in the x-y plane, and the other in the x-z plane. If the current in the loop is \(i\), what will be the resultant magnetic field due to the two semicircular parts at their common centre?

A current I is carried by an elastic circular wire of length L. It is placed in a uniform magnetic field B (out of paper) with its plane perpendicular to B's direction. What will happen to the wire?

          \(F ~\)

A particle with charge q, moving with a momentum p, enters a uniform magnetic field normally. The magnetic field has magnitude B and is confined to a region of width d, where $d<\frac{p}{Bq}$. The particle is deflected by an angle $\theta$ in crossing the field, then:

A particle of charge +q and mass m moving under the influence of a uniform electric field $\mathrm{E}\hat{\mathrm{i}}$ and a uniform magnetic field  $\mathrm{B}\hat{\mathrm{k}}$ follows a trajectory from P to Q as shown in the figure. The velocities at P and Q are $\mathrm{v}\hat{\mathrm{i}}$ and $-2\mathrm{v}\hat{\mathrm{j}}$ respectively. Which of the following statement(s) is/are correct?

A circular coil is in the y-z plane with its centre at the origin. The coil carries a constant current. Assuming the direction of the magnetic field at x = – 25 cm to be positive, which of the following graphs shows the variation of the magnetic field along the x-axis?

1.		2.
3.		4.

A current-carrying wire is placed in a uniform magnetic field in the shape of the curve \(y= \alpha sin ({\pi x \over L}),~0 \underline{<}x \underline{<}~2L\) $$
. What will be the force acting on the wire?
                   

A particle of charge q and mass m is moving along the x-axis with a velocity of v and enters a region of electric field E and magnetic field B as shown in the figure below. For which figure is the net force on the charge zero?

1.		2.
3.		4.

What is a representation of the magnetic field caused by a straight conductor with a uniform cross-section and a steady current of radius 'a'?

1.		2.
3.		4.