A) negative
B) \[\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{2{{q}^{2}}}{a}\]
C) \[\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{3{{q}^{2}}}{a}\]
D) zero
Correct Answer: D
Solution :
According to the question work done in increasing the separation from \[a\] to \[2a\] is \[W={{U}_{f}}-{{U}_{i}}\] Here, \[{{U}_{i}}=\frac{1}{4\pi {{\varepsilon }_{0}}}\left[ \frac{q(-2q)}{a}+\frac{q(-2q)}{a}+\frac{(-2q)(-2q)}{a} \right]\] \[=\frac{1}{4\pi {{\varepsilon }_{0}}a}[-2{{q}^{2}}-2{{q}^{2}}+4{{q}^{2}}]=0\] Similarly,\[{{U}_{f}}\]is also zero. Hence, \[W=0\]You need to login to perform this action.
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