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Magnetics question

2019 · 10 Jan · Shift 1 · Q54
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Magnetics question

2019 · 10 Jan · Shift 1 · Q54

JEE MainPhysicsMagneticsMCQ+4 / −1
An insulating thin rod of length lll has a linear charge density ρ(x)\rho \left( x \right)ρ(x)=ρ0xl{\rho _0}{x \over l}ρ0​lx​ 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 -
  1. A
    π3nρl3{\pi \over 3}n\rho {l^3}3π​nρl3
  2. B
    π4nρl3{\pi \over 4}n\rho {l^3}4π​nρl3
  3. C
    nρl3n\rho {l^3}nρl3
  4. D
    πnρl3\pi n\rho {l^3}πnρl3
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