A current is flowing in a long wire. It is first shaped as a circular coil of one turn and then into a coil of two turns of smaller radius. In which case the magnetic field produced at the centre will be stronger? And how much?

A straight wire carrying a current ${\mathrm{I}}_2$ is situated along the axis of a circular conductor carrying a current ${\mathrm{I}}_1$. What is the force produced due to the interaction between the two currents?

Imagine that you are sitting in a room filled with a uniform magnetic field pointing vertically downwards. At the centre of the room, two electrons are released horizontally with the same speed but in opposite directions. Describe their motion.

Imagine that you are sitting in a room filled with a uniform magnetic field pointing vertically downwards. At the centre of the room, two electrons are released horizontally with the same speed but in opposite directions. If one particle be electron and the other positron, then describe their motion.