JEE Main 2025 — Magnetic Properties Of Matter Question with Solution

(A) The unit "gauss" is used to measure magnetic induction, also known as magnetic flux density, within the CGS system of units.

$$B=\frac{\varphi }{A}=\frac{\max well}{c{m}^2}=gauss(CGS)$$

(B) Magnetic intensity (H) is defined as the product of the number of turns per unit length in a coil (n) and the current that it carries (I).

i.e. $$H=nI=\frac{N}{L}I$$

Unit : A/m or Am${}^{-1}$

(C) Magnetic flux, $$\varphi =BA$$

unit : weber

(D) Magnetic moment (M) : magnetic moment of a current loop, $$M=NIA$$

where, N = number of turns

I = current

A = Area

So, unit = Am${}^2$

Hence, option A is correct.