A) Zero having no direction
B) \[8F\] towards \[+\,q\] charge
C) \[8F\] towards \[-\,q\] charge
D) \[4F\] towards \[+\,q\] charge
Correct Answer: C
Solution :
Initially, force between A and C \[F=k\frac{{{Q}^{2}}}{{{r}^{2}}}\] When a similar sphere B having charge +Q is kept at the mid point of line joining A and C, then Net force on B is \[{{F}_{net}}={{F}_{A}}+{{F}_{C}}\]\[=k\frac{{{Q}^{2}}}{{{\left( {r}/{2}\; \right)}^{2}}}+\frac{k{{Q}^{2}}}{{{\left( {r}/{2}\; \right)}^{2}}}=8\frac{k{{Q}^{2}}}{{{r}^{2}}}=8F\]. (Direction is shown in figure)You need to login to perform this action.
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