Q 12-05-005NEETNEET 2020Top questionEasy
An iron rod of susceptibility $599$ is subjected to a magnetising field of $1200\ \text{A m}^{-1}$. The permeability of the material of the rod is : ($\mu_0 = 4\pi \times 10^{-7}\ \text{T m A}^{-1}$)
Answer: (A) $2.4\pi \times 10^{-4}\ \text{T m A}^{-1}$
Concept. Permeability depends only on the material: $\mu = \mu_0\mu_r = \mu_0(1 + \chi)$. The magnetising field is not needed.
Step 1. Relative permeability. $\mu_r = 1 + 599 = 600$.
Step 2. Permeability.
$$\mu = 4\pi \times 10^{-7} \times 600 = 2.4\pi \times 10^{-4}\ \text{T m A}^{-1}$$
Answer. $2.4\pi \times 10^{-4}\ \text{T m A}^{-1}$ (Option A).
Solution by Sreeraj P, M.Sc Physics