Q 12-05-026JEE MainJEE Main 2026 (4 Apr, Shift 2)Easy
A solenoid has a core made of material with relative permeability $400$. The magnetic field produced in the interior of solenoid is $1.0$ T. The magnetic intensity in SI units is $\alpha \times 10^5$. The value of $\alpha$ is ______.
(Free space permeability $\mu_0 = 4\pi \times 10^{-7}$ SI units.)
Answer: (B) $\dfrac{1}{16\pi}$
Concept. $B=\mu_0\mu_rH\Rightarrow H=\dfrac{B}{\mu_0\mu_r}$.
Step 1. Apply. $\dfrac{1}{4\pi\times10^{-7}\times400}=\dfrac{10^5}{16\pi}$ A/m.
Answer. $\alpha=\dfrac{1}{16\pi}$ (Option B).
Solution by Sreeraj P, M.Sc Physics
