The magnetism of a bar magnet is due to

Options

A. the earth
B. cosmic rays
C. the spin motion of electrons
D. pressure of big magnet inside the earth

Answer

C

Explanation

The magnetism of the magnet is due to the spin motion of electrons. Each electron in an atom is revolving in an orbit around the nucleus . The revolving electron is equivalent to a tiny loop of current . Therefore , it possesses some orbital magnetic dipole moment M = current ` xx ` area of the loop .
In addition to the orbital motion , every electron is assumed to have a spin motion around its axis . Therefore , another dipole magnetic moment called spin magnet `M_s` is also associated with electron . The vector sum of `M_l` and `M_s` provides the net magnetic dipole moment M to the atom . `M_s` is much greater than `M_l` , hence magnetism of magnet is due to spin motion of electrons .