If a bar magnet of pole strength m and magnetic moment M is cut equally 5 times parallel to its axis and again 3 times perpendicular to its axis, then the pole strength and magnetic moment of each piece are respectively.

Options

A. `(m)/(20) , (M)/(4)`
B. `m/5, (M)/(20)`
C. `m/6, (M)/(24)`
D. `m/5, (M)/(24)`

Answer

C

Explanation

A bar magnet that has been cut five times parallel to its axis will have six pieces of magnets having each magnetic strength `m. = m. l = m/6 l = M/6`
This bar magnet is also cut three times perpendicular to its axis. Pole strength, will remain m. =m/6 Again this bar magnet will have four pieces. Each piece has magnetic moment of this small magnet:
`M.. = M/6 xx l/4 = (ml)/(24) = (M)/(24)`