The Lorentz force depends upon the magnitude of the magnetic field.

A copper rod of mass $m$ slides under gravity on two smooth parallel rails $l$ distance apart and set an angle $\theta$ to the horizontal. At the bottom, the rails are joined by a resistance $R$ in figure. There is a uniform magnetic field $B$ perpendicular to the plane of the rails. The terminal velocity of rod is

The magnitude and direction of a force vector acting on a unit length of thin wire carrying a current $I$ at point $O$, if the wire has a semicircular shape of radius $R$ as shown in the figure.

$P, Q$ and $R$ form an equilateral triangle of side $10 \mathrm{cm}$ lying in the plane of the figure. Through each of the vertices an infinite wire passes perpendicular to this plane. The wire through $P$ carries a current of $10 \mathrm{A}$ going into the plane while the wires through $Q$ and $R$ carry $10 \mathrm{A}$ current coming out of the plane.

The force per unit length on the wire through $P$ is

Lorentz force is given by: (symbols have their usual meanings)

What is the net force on the square coil?

Let $F_A$ and $F_B$ be the magnitude of the force between the two wires in setup $A$ and setup $B$, respectively.