Question

A bar magnet has been cut equally lengthwise and widthwise to give four equal pieces.The pole strength of each piece as compared to the pole strength of original bar magnet is

• A. Same
• B. $\frac{1}{8}$
• C. $\frac{1}{4}$
• D. $\frac{1}{2}$

Answer 1

The correct option is D $\frac{1}{2}$

Answer is D.
Magnetic properties of a magnet are due to the alignment of electrons in a particular direction. When a magnet is cut into two halves the number of electrons in total and in a particular direction become less than the initial so the magnetic field of a magnet becomes less.
Magnetic strength depend on magnetic dipole moment of a magnet (M = m*l) which depends linearly on length. So, their magnetic strength reduces linearly in the same proportion as that of its length reduces.
Hence, the pole strength of each piece as compared to the pole strength of original bar magnet is reduced by half, that is, 1/2.