A) ? q
B) \[-\,2q\]
C) \[-\frac{q}{2}\]
D) \[4q\]
Correct Answer: A
Solution :
The force between 4q and q; \[{{F}_{1}}=\frac{1}{4\pi {{\varepsilon }_{0}}}\cdot \frac{4q\times q}{{{l}^{2}}}\] The force between Q and q; \[{{F}_{2}}=\frac{1}{4\pi {{\varepsilon }_{0}}}\cdot \frac{Q\times q}{{{(l/2)}^{2}}}\] We want \[{{F}_{1}}+{{F}_{2}}=0\] or \[\frac{4{{q}^{2}}}{{{l}^{2}}}=-\frac{4Qq}{{{l}^{2}}}\] Þ \[Q=-q\]You need to login to perform this action.
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