Conclusion

Coulomb’s law for the force bold cap f sub 12on a point charge q sub one due to a point charge q sub two can be written as

multiline equation line 1 bold cap f sub 12 equals one divided by four times pi times epsilon sub zero times q sub one times q sub two divided by r sub 12 squared times r hat sub 12 comma

where epsilon sub zero is the permittivity of free space, r sub 12 is the magnitude of the displacement from charge q sub two to charge q sub one, and r hat sub 12 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.

OpenLearn - Electromagnetism: testing Coulomb’s law
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