question_answer

Two small spheres each having the charge \[+Q\] are suspended by insulating threads of length \[L\] from a hook. This arrangement is taken in space where there is no gravitational effect, then the angle between the two suspensions and the tension in each will be         [IIT 1986]

A)                    \[{{180}^{o}},\,\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{Q}^{2}}}{{{(2L)}^{2}}}\]              

B)                    \[{{90}^{o}},\,\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{Q}^{2}}}{{{L}^{2}}}\]

C)                    \[{{180}^{o}},\,\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{Q}^{2}}}{2{{L}^{2}}}\] 

D)                    \[{{180}^{o}},\,\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{Q}^{2}}}{{{L}^{2}}}\]

Correct Answer: A

Solution :

(a) The position of the balls in the satellite will become as shown below                    Thus angle q = 180° and Force \[=\frac{1}{4\pi {{\varepsilon }_{0}}}\cdot \frac{{{Q}^{2}}}{{{(2L)}^{2}}}\]