8.1 Electric Charge and Electric Force

Charge

Charge is a fundamental property of matter similar to mass. Unlike mass, there are two types of charge, and we call them “ positive charge ” and “ negative charge ”. The SI unit for charge is the coulomb (C).

By convention we assign electrons as carrying negative charges and protons as carrying positive charges. Electrons are fundamental particles and cannot be further divided, and therefore the magnitude of the charge of an electron is called the elementary charge (${e=1.6 \cdot 10^{-19} C}$) . The charges of a proton and electron are ${e}$ and ${-e}$, respectively. Since electrons cannot be broken down, charge is quantized: all charges are integer multiples of the elementary charge. An object’s net charge is the total sum of the charges within the object.