Question

The sum of the two point charges is 7microCoulomb. They repel each other with a force of 1N when kept 30cm apart in free space. Calculate the value of each charge?

It would be great if you could explain step by step. :)

Answer 1

As,they repel each other,they must be like charges.

Let,they be `q1` and `q2`

Given, `q1+q2=7*10^-6`

Now, if `1N` force is acting in between them on keeping them `30 cm` apart,then

`1 = 9*10^9*q1*(q2)/(30/100)^2`

or, `q1q2 = 10^-11`

Now, `(q1-q2)^2 = (q1+q2)^2-4q1q2`

so, `(q1-q2) = sqrt(9*10^-12) =3*10^-6`

So,solving the equations, we get, `q1=5*10^-6 C` and `q2=2*10^-6 C` (note,both can be negative together as well)