Electric Force is a Vector

Now, consider these two situations together. We will use subscripts q₂ and q₃ to distinguish the two charges q that exert forces on charge Q which we will now label as Q₁.

Remember the "Free Body Diagrams" we used in our earlier study of forces in Mechanics? We will need them again here. We are going to concentrate on what is happening to one charge, Q₁. Calculate, draw, and label all the forces that act on Q₁.

Look only at the forces acting on charge Q₁; those are forces F₁₂ and F₁₃,

These are the magnitudes of forces F₁₂ and F₁₃. Remember that forces always add as the vectors they are:

 

Coulomb's Law			Numerical Example
Return to Ch 17, Electrostatics & Electric Energy

(c) Doug Davis, 2002; all rights reserved