Superposition of forces

Intermediate

Net force is the vector sum from each charge.

The force on a charge due to several others is the vector sum of the individual Coulomb forces. Each pair interacts independently.

Worked example

A charge at the centre of a symmetric ring of equal charges feels zero net force.

Common mistake

Add components, not magnitudes.

In more detail

The net electric force on a charge from several others is the vector sum of the individual forces, found by resolving into components.

Calculating the force on a particle in a complex charge arrangement.
Modelling ions in solution as sums of forces.
Engineers calculating the force on a charged particle near several charges add the individual forces as vectors.

Do forces add like vectors?

Yes, electric forces obey superposition, so you add them as vectors.

Can I add magnitudes?

Only if they act along the same line, otherwise you must resolve them.

Do I add forces or magnitudes?

Always add vectors, using components. Adding magnitudes ignores direction and gives the wrong answer.