We considered F to be the force between the charges, and realized that, by Newton's third law, the force on charge q 1 was equal and opposite to the force on charge q .
All forces are vectors, of course, and the electric force is no exception.
Our scalar equation does not seem to assign a direction to the force, but we can do that by remembering that opposite charges attract, and like charges repel. Now let's consider the vector F to be the force on q due to q 1 . Again we can write this as where the sum is a vector sum. We can break up the source distribution into many small pieces of charge, and add up all their contributions to the electric field. All Rights Reserved.