What is an electric motor? State it's principle.

State two ways by which the speed of rotation of an electric motor can be increased.

A copper wire is held between the poles of a magnet. There is a switch provided to reverse the current in the wire. Also, the polarity can be changed. In how many directions can the force act on the wire?

The given figure shows the path of three particles A, B and C in a uniform magnetic field (perpendicular to the plane of paper outwards). Identify the nature of charges on them. Name the rule you have used