Question

a point charge q is kept at the centre of a fixed semicircular thread having a uniform charge per unit length lamda the radius of the semicircular thread being R. the force required to keep the charge stationary is

Answer 1

Answer:

Force required is 2kqa/r

Explanation:

Point kept at centre = q

Radius = R

Charge at the segment rdθ =ardθ

The horizontal component of force will be cancelled out as the ring will be symmetric about y axis

Vertical force =Fcosθ =kqardθ/r2Cosθ

                                   =kqa/r cosθ dθ

Thus, total force = limit 0 to 90, 2∫ kqa/r cosθ dθ  

                              = limit 0 to 90,  2kqa/r∫ cosθ dθ  

                             = 2kqa/r

Answer 2

Answer:

Your answer is F = q lambda/ 2piEr

Explanation: PLz refer to the attachment for explanation