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Points A and B are at potentials $+7\ V$ and $-4\ V$. The work done in moving 50 electrons from A to B is
A$-8.8\times10^{-17}\ J$
B$8.8\times10^{-17}\ J$
C$4.4\times10^{-17}\ J$
D$1.1\times10^{-16}\ J$
Answer & Solution
Correct answer: B. $8.8\times10^{-17}\ J$
1. Charge moved: $|q| = 50\times1.6\times10^{-19} = 8.0\times10^{-18}$ C (electrons).
2. Potential difference magnitude: $V_A - V_B = 7-(-4) = 11$ V.
3. Work $= |q|\,|V_A - V_B| = 8.0\times10^{-18}\times11 = 8.8\times10^{-17}$ J.
_Source: Samacheer Kalvi Class 12 Physics Vol.1, Unit 1 'Electrostatics', Evaluation Q.11_
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