(a) Describe an activity to show the magnetic field lines formed by a current-carrying circular coil.
(b) Draw the magnetic field lines due to current-carrying circular coil.

Explanation

(a) Take a rectangular cardboard sheet. Make two holes in it at a suitable distance. Insert a circular coil having large number of turns of enamelled copper wire passing through these holes so that the coil is normal to the plane of cardboard.
Complete the electric circuit [Fig. 13.20] by joining ends of the coil with a battery and a key K. Sprinkle iron-filings uniformly on the carboard. Plug the key and gently tap the cardboard. The iron-filings arrange themselves along the magnetic field lines. The pattern of iron-tilings gives the magnetic field lines due to current-carrying circular coil.
(b) See Fig. 13.4.