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Question: Answered & Verified by Expert
A long solenoid carrying a current produces a magnetic field $B$ along its axis. If the current is doubled and the number of turns per $\mathrm{cm}$ is halved, the new value of the magnetic field is:
PhysicsMagnetic Effects of CurrentNEETNEET 2003
Options:
  • A $\frac{B}{2}$
  • B $B$
  • C $2 B$
  • D $4 B$
Solution:
1373 Upvotes Verified Answer
The correct answer is: $B$
Magnetic field induction at point insides the solenoid of length $l$, having $n$ turns per unit length carrying current $i$. is given by
$$
B=\mu_0 n i
$$
If $i$ is double and $n$ is halved then $B$ remains same.

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