Conclusion

Coulomb’s law for the force on a point charge due to a point charge can be written as

where is the permittivity of free space, is the magnitude of the displacement from charge to charge , and is the unit vector for this displacement.

You can use this form of Coulomb's law repeatedly with vector addition to find the force on a point charge due to a system of a few charges. However, when considering more complicated systems of charges or continuous charge distributions it is usually necessary to use computer based methods to determine the resulting force.

This OpenLearn course is an adapted extract from the Open University course SM381 Electromagnetism [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] .