JEE Main · PhysicsHard

A solenoid of length $L$ and radius $R$ has $n$ turns per unit length. It carries a current $I$. What is the magnetic field $B$ at the center of the solenoid if it is very long ($L >> R$)?

  1. A.$\frac{\mu_0 n I}{2}$
  2. B.$\mu_0 n I$
  3. C.$2\mu_0 n I$
  4. D.$\frac{\mu_0 n I}{4}$
Show correct answer & step-by-step solution

Correct answer: B$\mu_0 n I$

Solution

Using Ampere's Law, . For along solenoid, , which simplifies to .

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