A uniformly charged non-conducting disc of radius R and total charge Q rotates with angular speed ω. What is its magnetic dipole moment?
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A uniformly charged non-conducting disc of radius R and total charge Q rotates with angular speed ω. What is its magnetic dipole moment?

G1 Physics · Accepted Answer

For surface charge density σ=Q/(πR²), a ring of radius r has dq=2πσrdr, dI=ωdq/(2π), and dμ=dI·πr². Integration gives μ=QωR²/4.