A charge of +3.0 µC is distributed uniformly along the circumference of a circle with a radius of 20 cm. How much external energy is required to bring a charge of 25µC from infinity to the center of the circle?

The energy required is  

Explanation:

From the question we are told that

  The charge is

  The radius is

   The second charge is

Generally the energy required is mathematically represented as

Where k is the coulomb constant with a value of  

       Substituting values we have

it becomes positively charged by charging it

if they have a finite resultant