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JEE Main 20264 AprilEvening Shift
Exam
JEE Main
Year
2026
Date
4 April
Shift
Evening Shift
Subject
Physics
Chapter
Magnetic Properties of Matter

JEE Main 2026 · 4 April · Evening Shift · Physics · Magnetic Properties of Matter

A solenoid has a core made of material with relative permeability...

A solenoid has a core made of material with relative permeability 400400. The magnetic field produced in the interior of solenoid is 1.01.0 T. The magnetic intensity in SI units is α×105\alpha \times 10^5. The value of α\alpha is ______.
(Free space permeability μ0=4π×10−7\mu_0=4\pi \times 10^{-7} SI units.)

Options

  1. A25π\dfrac{25}{\pi}
  2. B116π\dfrac{1}{16\pi}
  3. C1π\dfrac{1}{\pi}
  4. D14π\dfrac{1}{4\pi}

Correct answer

B. 116π\dfrac{1}{16\pi}

Step-by-step solution

The magnetic field BB inside the solenoid is related to the magnetic intensity HH by the formula:

B=μH=μ0μrHB = \mu H = \mu_0 \mu_r H

Rearranging for HH, we get:

H=Bμ0μrH = \dfrac{B}{\mu_0 \mu_r}

Substituting the given values (B=1.0B = 1.0 T, μr=400\mu_r = 400, and μ0=4π×10−7\mu_0 = 4\pi \times 10^{-7} T m/A):

H=1.04π×10−7×400H = \dfrac{1.0}{4\pi \times 10^{-7} \times 400}

H=1.01600π×10−7H = \dfrac{1.0}{1600\pi \times 10^{-7}}

H=116π×10−5H = \dfrac{1}{16\pi \times 10^{-5}}

H=116π×105H = \dfrac{1}{16\pi} \times 10^5 A/m

Comparing this with the given expression H=α×105H = \alpha \times 10^5, we find:

α=116π\alpha = \dfrac{1}{16\pi}

Answer: 116π\dfrac{1}{16\pi}
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