Physics · 2019
JEE Main · 10 January 2019, Shift 1 · Q20
An insulating thin rod of length l has a linear charge density ρ(x)=ρ_0 x/l on it. The rod is rotated about an axis passing through the origin (x=0)…
An insulating thin rod of length $\displaystyle l$ has a linear charge density $\displaystyle \rho(x)=\rho_0 \frac{x}{l}$ on it. The rod is rotated about an axis passing through the origin $\displaystyle (x=0)$ and perpendicular to the rod. If the rod makes n rotations per second, then the time averaged magnetic moment of the rod is :
Official answer
(4)
$\displaystyle \frac{\pi}{4} \mathrm{n} \rho l^3$
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JEE Main 2019 Physics question, with the answer from NTA’s final answer key. Where our answers come from.