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1. Electric Charges and Fields
medium
Two similar spheres having $ + \,q$ and $ - \,q$ charge are kept at a certain distance. $F$ force acts between the two. If in the middle of two spheres, another similar sphere having $ + \,q$ charge is kept, then it experience a force in magnitude and direction as
A
Zero having no direction
B
$8F$ towards $ + \,q$ charge
C
$8F$ towards $ - \,q$ charge
D
$4F$ towards $ + \,q$ charge
Solution
(c) 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}}}{{{{(r/2)}^2}}} + \frac{{k{Q^2}}}{{{{(r/2)}^2}}} = 8\frac{{k{Q^2}}}{{{r^2}}} = 8F$
(Direction is shown in figure)
Standard 12
Physics
