The surface charge density of a thin charged disc of radius R is σ. The value of the electric field at the centre of the disc is 2∈0σ. With respect to the field at the centre, the electric field along the axis at a distance R from the centre of the disc:
Held on 25 Apr 2013 · Verified 6 Jul 2026.
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A short bar magnet placed with its axis at $30^{\circ}$ with an external field of 800 Gauss, experiences a torque of $0.016 \mathrm{~N}. \mathrm{m}$. The work done in moving it from most stable to most unstable position is $\alpha \times 10^{-3} \mathrm{~J}$. The value of $\alpha$ is $\_\_\_\_$.
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