Electric charge and elementary charge

Summary

Electric charge is a fundamental property of matter (and antimatter) that creates and responds to electric forces. By modern convention, electrons carry negative charge and protons carry positive charge. Charge comes in two opposing signs and produces electrostatic effects such as attraction between opposite charges and repulsion between like charges; these interactions are quantified by Coulomb’s law, which gives the force based on the product of charges and the inverse-square dependence on distance. The elementary charge is the smallest unit of electric charge: it is defined as the magnitude of the charge on a proton (and the equal magnitude on an electron with opposite sign). Numerically, it is 1.602176634 × 10⁻¹⁹ coulombs, and any measurable charge on an object is always a whole-number multiple of this value. Charge is also conserved: in an isolated system, the net total charge remains constant even as charge is transferred between bodies (for example, by contact or through conductors).

Key Points

• 1

  Electric charge exists in positive and negative forms and produces forces described by Coulomb’s law.

• 2

  The elementary charge (1.602176634 × 10⁻¹⁹ C) is the fundamental unit; all charges are integer multiples of it.

• 3

  Electric charge is conserved in isolated systems and can be transferred between objects via contact or conduction.