Magnetic Effects of Curre question bank (Physics)

A circular current carrying coil has radius $\mathrm{R}$. At what distance from the centre of the coil on the axis, the magnetic induction will become $\frac{1}{8}$ th of its value at the centre of the coil?

A bar magnet of magnetic moment $5 \mathrm{Am}^{2}$ is placed in a uniform magnetic induction $3 \times 10^{-5} \mathrm{~T}$. If each pole of a magnet experiences a force of $2 \cdot 5 \times 10^{-4} \mathrm{~N}$ then the magnetic length of the magnet is