A paramagnetic substance in the form of a cube with sides 1 cm has a magnetic dipole moment of $20 \times 10^{-6} \mathrm{~J} / \mathrm{T}$ when a magnetic intensity of $60 \times 10^{3} \mathrm{~A} / \mathrm{m}$ is applied. Its magnetic susceptibility is:

JEE Main · 2019 · 11 Jan 2019 · Shift 2 · Magnetic Properties of Matter

A paramagnetic substance in the form of a cube with sides 1 cm has a magnetic dipole moment of

20 \times 1 0^{- 6} J / T

when a magnetic intensity of

60 \times 1 0^{3} A / m

is applied. Its magnetic susceptibility is:

Answer: (D)

The intensity of magnetisation is the magnetic moment per unit volume,

I = \frac{M}{V}

. For a cube of side

1 cm

the volume is

V = (1 0^{- 2})^{3} = 1 0^{- 6} m^{3}

, so

I = \frac{20 \times 1 0 ^{- 6}}{1 0 ^{- 6}} = 20 A/m

. The magnetic susceptibility is the ratio of the magnetisation to the applied magnetic intensity,

χ = \frac{I}{H} = \frac{20}{60 \times 1 0 ^{3}} = 3.3 \times 1 0^{- 4}

JEE Main · 2019 · 11 Jan 2019 · Shift 2 · Single correct option