List three sources of magnetic fields.

How is the induced current in a secondary coil related to the current in a primary coil?

The phenomenon of electromagnetic induction is:

$(a)$ Describe an activity to show the pattern of magnetic field lines of a bar magnet,with the help of a cardboard piece and iron filings.
$(b)$ Compare the magnetic field of a bar magnet with that of a current-carrying solenoid with the help of a figure.

State whether the following statements are true $(T)$ or false $(F)$.
$(a)$ An electric motor converts mechanical energy into electrical energy.
$(b)$ An electric generator works on the principle of electromagnetic induction.

$(a)$ Magnetic field lines of two bar magnets $A$ and $B$ are as shown below. Name the poles of the magnets facing each other.
$(b)$ Two magnetic field lines never intersect each other. Why?
$(c)$ How does the strength of the magnetic field at the centre of a current-carrying circular coil depend on the
$(i)$ radius of the coil,
$(ii)$ number of turns in the coil, and
$(iii)$ strength of the current flowing in the coil?