Draw the field lines of (a) a bar magnet (b) a current carrying finite solenoid, and (c) an electric dipole.
What basic difference do you notice between the magnetic and electric field lines? How do you explain this difference?

Solution

The field lines of (a) a bar magent, (b) a current carrying finite solenoid and (c) electric dipole are shown below.
At large distances, the field lines are very similar. The curves labelled (i) and (ii) are closed Gaussian surfaces.

There is a basic difference between magnetic and electric field lines. In case of the electric field of an electric dipole, the electric lines of force originate from positive charge and end at the negative charge.
In case of a bar magnet, the magnetic field lines are closed loops, i.e., magnetic field lines do not start or end anywhere.