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Moving Charges And Magnetism

Question
CBSEENPH12039966

Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency f Hz. The magnitude of magnetic induction at the centre of the ring is 

  • μoqf  / 2R

  • μoq / 2fR

  • μoq / 2πfR

  • μoqf / 2πR

Solution

A.

μoqf  / 2R

B = μoi / 2R
q = it 
 ⇒ i = q /t = qf
B = μoqf  / 2R