Which of the following statements are correct?(A) Magnetic susceptibi…

The correct answer is Option (2) → (A) and (B) only

The magnetic susceptibility \( \chi \) of a material is defined by \( \vec{M} = \chi\vec{H} \), so \( \chi = M/H \), the ratio of the intensity of magnetisation to the magnetic intensity.

(A) Magnetic susceptibility is defined as ratio of Intensity of magnetisation to magnetic field intensity. — Correct. This is \( \chi = M/H \).

(B) Magnetic susceptibility is a ratio of similar quantities therefore has no unit. — Correct. M and H both have the unit \( \mathrm{A\,m^{-1}} \), so the ratio is dimensionless.

(C) The value of magnetic susceptibility for vacuum is one. — Incorrect. There is no magnetisation in vacuum, so \( \chi = 0 \). It is the relative permeability \( \mu_r = 1 + \chi \) that equals 1 for vacuum.

(D) Greater is the value of intensity of magnetisation, smaller is the value of susceptibility. — Incorrect. For the same H, a larger M means a larger \( \chi = M/H \), not a smaller one.

(E) Smaller is the value of magnetic field intensity, smaller is value of susceptibility. — Incorrect. \( \chi \) is a property of the material; when H is made smaller, M falls in the same proportion and the ratio stays the same.

NCERT (2026-27):
Magnetisation and Magnetic Intensity – “… This influence is mathematically expressed as

    \( \displaystyle \mathbf{M} = \chi\,\mathbf{H} \qquad (5.13) \)

where \( \chi \), a dimensionless quantity, is appropriately called the magnetic susceptibility. It is a measure of how a magnetic material responds to an external field.”

Magnetisation and Magnetic Intensity – “… where \( \mu_r = 1 + \chi \), is a dimensionless quantity called the relative magnetic permeability of the substance.”