Charge and Electric Force

The proton has a charge of +1.602 10^-19 coulombs (C), while the electron has a charge of -1.602 × 10^-19 C. The neutron has zero charge. Electric charge and, more so, its movement are the most basic items of interest in electrical engineering. When many charged particles are collected together, larger charges and charge distributions occur. There may be point charges (C), line charges (C/m), surface charge distributions (C/m²), and volume charge distributions (C/m³).

A charge is responsible for an electric ?eld and charges exert forces on each other. Like charges repel, whereas unlike charges attract. Such an electric force can be controlled and utilized for some useful purpose. Coulomb's law gives an expression to evaluate the electric force in newtons (N) exerted on one point charge by the other:

1. Forces ¯ F₂₁ and ¯ F₁₂ are experienced by Q1 and Q2, due to the presence of Q2 and Q1, respectively. They are equal in magnitude and opposite of each other in direction.

2. The magnitude of the force is proportional to the product of the charge magnitudes.

3. The magnitude of the force is inversely proportional to the square of the distance between the charges.

4. The magnitude of the force depends on the medium.

5. The direction of the force is along the line joining the charges.