Question 752: Electrostats & Capacitance

Question

Two small spheres each of mass 10 mg are suspended from a point by threads 0.5 m long. They are equally charged and repel each other to a distance of 0.20 m. The charge on each of the sphere is $${a \over {21}} 	imes {10^{ - 8}}$$C. The value of 'a' will be ___________. [Given g = 10 ms$$-$$2]

Accepted Answer

T sin$$	heta$$ = $${{k{q^2}} \over {{r^2}}}$$
T cos$$	heta$$ = mg
tan$$	heta$$ = $${{k{q^2}} \over {mg{r^2}}}$$
q
2
= $${{	an 	heta mg{r^2}} \over k}$$
$$ \because $$ tan$$	heta$$ = $${{0.1} \over {0.5}} = {1 \over 5}$$
$${q^2} = {1 \over 5} 	imes {{10 	imes {{10}^{ - 6}} 	imes 10 	imes 0.2 	imes 0.2} \over {9 	imes {{10}^9}}}$$
$$q = {{2\sqrt 2 } \over 3} 	imes {10^{ - 8}}$$
after comparison from the given equation a = 20

Electrostats & Capacitance

Two small spheres each of mass 10 mg are suspended from a point by threads 0.5 m long. They are equally charged and repel each other to a distance of 0.20 m. The charge on each of the sphere is ${a \over {21}} \times {10^{ - 8}}C. The value of 'a' will be ___________. [Given g = 10 ms-$2]

Choose the correct answer: