A magnetic needle of negligible breadth and thickness compared to its length, oscillates in a horizontal plane with a period $T$. The period of oscillation of each part obtained on breaking the magnet into $n$ equal parts perpendicular to the length is

Two identical short bar magnets, each having magnetic moment of $10\, Am^2$, are arranged such that their axial lines are perpendicular to each other and their centres be along the same straight line in a horizontal plane. If the distance between their centres is $0.2 \,m$ , the resultant magnetic induction at a point midway between them is$({\mu _0} = 4\pi \times {10^{ - 7}}\,H{m^{ - 1}})$

A closely wound solenoid of $800$ turns and area of cross section $2.5 \times 10^{-4} \;m ^{2}$ carries a current of $3.0\; A .$ Explain the sense in which the solenoid acts like a bar magnet. What is its associated magnetic moment?

A magnet of magnetic moment $M$  and pole strength $m$  is divided in two equal parts, then magnetic moment of each part will be

The unit of magnetic moment is

Magnetic moments of two bar magnets may be compared with the help of