A) 11J
B) 1.1J
C) 0.01 J
D) 0.1 J
Correct Answer: C
Solution :
(c) 0.01 J Initial PE of the three charges, \[{{U}_{i}}k\frac{{{q}_{1}}{{q}_{2}}+{{q}_{2}}{{q}_{3}}+{{q}_{1}}{{q}_{3}}}{r}\] \[=9\times {{10}^{9}}\left[ \frac{1\times 2\times {{10}^{-12}}+2\times 3\times {{10}^{-12}}+1\times 3\times {{10}^{-12}}}{1} \right]\]\[=99\times {{10}^{-3}}\,J\] Final PE of the system \[{{U}_{f}}=9\times {{10}^{9}}\left[ \frac{1\times 2\times {{10}^{-12}}+2\times 3\times {{10}^{-12}}+1\times 3\times {{10}^{-12}}}{1} \right]\]\[=\frac{99\times {{10}^{-3}}}{0.5}=198\times {{10}^{-3}}J\] \[W={{U}_{f}}-{{U}_{i}}=\left( 198-99 \right)\times {{10}^{-3}}J\] \[=99\times {{10}^{-3}}J=0.099=0.01\,J\]You need to login to perform this action.
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