Two small spherical balls each carrying a charge `Q= 10 mu C`( 10 micro=coulomb) are suspended by two insulating threads of equal lengths `1 cm` each, from a point fixed in the ceiling. It is found that in equilibrium threads are sepreated by an angle `60^(@)` between them, as shown in figure. What is the tension in the threads
(Given `(1)/(4piepsilon_(0))= 9xx10^(9)Nm//C^(2)` )

Options

A. `18 N`
B. `1.8 N`
C. `0.18 N`
D. None of the above

Answer

b

Explanation

In the following figure, in equilibrium `F_(e)= T sin 30^(@) r=1`

`= 9xx10^(9).(Q_(2))/(r^(2))=Txx1/2`
`implies 9xx10^(9).((10xx10^(-6))^(2))/(1^(2))= Txx1/2implies T= 1.8 N`