A bar magnet has a magnetic moment equal to 5 10⁻⁵ ~Wb - m . It is suspended in a magnetising field equal to 8 10⁻⁴ ~A - m ⁻¹ . The magnet vibrates with a period 15 s . The moment of inertia of the magnet is:

Step-by-step solution

The SI unit of magnetic moment is A - m ^2 , but the magnetic moment is given in Wb - m ^2 , which is the unit of ₀ M . aligned ₀ M & =5 10⁻⁵ M & = 5 10⁻⁵ ₀ ~Wb - m & = 5 10⁻⁵ 4 10⁻⁷ = 125 aligned As T=2 I M B aligned I & = T^2 M B 4 ^2 = (15)^2 ( 125 ) 8 10⁻⁴ 4 ^2 & =0.57 ~kg ~m ^2 aligned