JEE Main 2026 · 4 Apr · Shift 2 · Physics Q39

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PhysicsSingle correct+4 / -1Question 39 of 75

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 $\alpha\times10^5$ . The value of $\alpha$ is ________.
(Free space permeability $\mu_0=4\pi\times10^{-7}$ SI units.)

\dfrac{25}\pi

\dfrac1{16\pi}

\dfrac1\pi

\dfrac1{4\pi}

Answer and worked solution

Official answer: B

Magnetic intensity.
$H=\frac B{\mu_0\mu_r}=\frac1{4\pi\times10^{-7}\times400}=\frac{10^5}{16\pi}\text{ A/m},$
so $\alpha=\dfrac1{16\pi}$ .

(B)

Topics:Ampere's circuital law

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JEE Main 2026 · 4 Apr · Shift 2, Physics question 39