JEE Main 2019PhysicsMagnetic Effects of CurrentMediumMCQ

JEE Main 2019 — Magnetic Effects of Current Question with Solution

JEE Main 2019 (10 Jan Shift 1)

Question

An insulating thin rod of length l has a linear charge density ρx=ρ0xl on it. The rod is rotated about an axis passing through the origin x=0 and perpendicular to the rod. If the rod makes n rotations per second, then the time averaged magnetic moment of the rod is:

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Show full solutionCorrect option: A
Correct answer
Aπ4n ρ0l3

Step-by-step explanation

ω=2πn rad s-1



dQ=ρ dx

=ρ0lxdx

Current due to elementary charge dQ

dI=dQ ω2π 

Magnetic dipole moment

dM=dI×A

∫dM=∫0lω2π×ρ0l×xdx πx2

M=π nρ0l34

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About this question

This is a previous-year question from JEE Main 2019, covering the Magnetic Effects of Current chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.