Reference Tools and Resources

I. Key Terms and Phrases

electric charge a property of particles that is important to the structure of atoms and molecule and acts as the source of a fundamental force of nature

Coulomb’s law the force law between two point charges

electrostatics the phenomena associated with the forces between static charges

electrically neutral the situation in which an object has no net electric charge

conductors materials, such as metals, in which electrons easily flow

insulators materials, such as rubber, in which electrons do not readily flow

semiconductors materials with electrical properties intermediate between conductors and insulators

coulomb (C) the SI unit of electric charge

protons positively charged particles, in atomic nuclei, that posses the smallest measurable electric charge

electrons negatively charged particles found in atoms that posses the smallest measurable electric charge

neutrons particles, in atomic nuclei, that are electrically neutral

conservation of charge the principle that the net charge is the same before and after any interaction

charge quantization the fact that electric charge only occurs in integral multiples of an elementary amount of charge

principle of superposition the principle that electrical forces that result from multiple sources are obtained by vector addition of the results from the individual sources

charge density a measure of the compactness of electric charge that is especially useful with continuous charge distributions

II. Important Equations

Name/Topic	Equation	Explanation
Coulomb's Law		The electrical force exerted on q1 due to q2; is a unit vector pointing from q2 toward q1.
Principle of Superposition		The net electrical force on a point charge q due to N other point charges;is a unit vector pointing from qi toward q.
Principle of Superposition		The net electrical force on a point charge q due to continuous charge distributions. The three cases considered are for continuous charges distributed on a line, over a surface, and throughout a volume, respectively.

III. Know Your Units

Quantity	Dimension	SI Unit
Electric Charge ( q )	[C]	C
Permittivity of Free Space ( )