Question

A test charge is introduced into the electric field of a charge. It feels a force of 2F where the electric field is 2E. What would the force on the test charge be where the electric field is 8E?
Somebody explain how you would get the answer.

Answer 1

We know, q = F / E
q = 2 / 4 
q = 1/2

Now, we have: q = 1/2 and E = 1
Substitute the value into the expression:
F = E.q
F = 1/2 * 1 = 1/2

In short, Your Answer would be 1/2

Answer 2

Surrounding every charge (or group of charges) is a thing, called an electric field. (it is a vector thing). E. Definition: The electric field at a point. E in empty space is a vector quantity which can be measured by the following procedure: place a small test charge q at that point, measure the force on q due to all other charges.