In which of the following devices is an electric motor $NOT$ used?

How does the strength of the magnetic field at the centre of a circular coil of wire depend on: $(i)$ the radius of the coil $(ii)$ the number of turns of wire in the coil $(iii)$ the strength of the current flowing in the coil?

Describe the working of an $AC$ generator with the help of a labelled circuit diagram. What changes must be made in the arrangement to convert it to a $DC$ generator?

Magnetic field lines of two magnets are shown in figures $A$ and $B$. Select the figure that represents the correct pattern of the field lines. Give reasons for your answer. Also,name the poles of the magnets facing each other.

Name the factors on which the force acting on a current-carrying conductor placed in a magnetic field depends.

Differentiate between overloading and short-circuiting.