Magnetic field due to currentHard
Question
A thin circular disk of radius R is uniformly charged with density σ > 0 per unit area. The disk rotates about its axis with a uniform angular speed ω. The magnetic field at centre of the disk is :-
Options
A.μ0Rωσ
B.
μ0Rωσ
μ0RωσC.
σω
σωD.
σω
σωSolution
Let a ring of radius x and width dx.
Assume charge on ring is dq
Area of ring dA = 2π x dx
σ =
⇒ dq = σ2π x dx
Current due to this ring dI =
dI = ω σ x dx
Magnetic field due to ring at centre dB =
=
μ0σωdx
Magnetic field due to disc at centre
B =
μ0σω 
μ0 σωR
Assume charge on ring is dq
Area of ring dA = 2π x dx
σ =
⇒ dq = σ2π x dxCurrent due to this ring dI =
dI = ω σ x dx
Magnetic field due to ring at centre dB =
=
μ0σωdxMagnetic field due to disc at centre
B =
μ0σω μ0 σωRCreate a free account to view solution
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