Question

A cylindrical magnetic rod has length 5 cm and diameter 1 cm. It has uniform magnetization `5.3 xx 10^3 "A"/"m"^3`. Its net magnetic dipole moment is nearly `(pi = 22/7)`.

Options

• `2.5 xx 10^-2 "J"/"T"`

• `10^-2 "J"/"T"`

• `0.5 xx 10^-2 "J"/"T"`

• `2 xx 10^-2 "J"/"T"`

Answer 1

`2 xx 10^-2 "J"/"T"`

Explanation:

Volume of the rod = `pi "d"^2/4 * l = pi(0.01)^2/4 xx 0.05`

Magnetisation = `"magnetic moment"/"volume"`

`therefore "magnetic moment" = "magnetization" xx "volume"`

`= 5.3 xx 10^3 xx 22/7 xx 1/4 xx 1/10^4 xx 5/100`

`= (53 xx 22 xx 5)/28 xx 10^-4`

`= 2.08 xx 10^-2`

`= 2 xx 10^-2`J/T