Verified Solution • 2025–26 Session moderate

QJEEM22Ph50fa: JEE Main 2022 Physics - Class 12 JEEM22Ph50fa Solution: A long solenoid carrying a current produces a magnetic field B…

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 cm is halved, the new value of magnetic field will be equal to

Multiple Choice Options

  • A B
  • B 2B
  • C 4B
  • D B2{B \over 2}

Step-by-Step Verified Solution

B=μ0niB = {\mu _0}ni

Now i→2ii \to 2i

And n→n2n \to {n \over 2}

B′=μ0n2×2i=μ0ni=BB' = {\mu _0}{n \over 2} \times 2i = {\mu _0}ni = B

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