A thin wire is bent into a circular ring of radius 10 cm. A charge of 250 μC spreads uniformly over it. The electric potential at the centre of the ring is:
A$2.25 \times 10^7$ V
BZero
C$1.125 \times 10^7$ V
D$2.25 \times 10^5$ V
Answer & Solution
Correct answer: A. $2.25 \times 10^7$ V
Every element of charge on the ring is at the same distance R from the centre, so $V = (1/4\pi\varepsilon_0)\,q/R = (9\times10^9)(250\times10^{-6})/0.1 = 2.25\times10^7$ V. (The field at the centre is zero by symmetry, but V is not.)
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