# Electronics/Expanded Edition Fundamentals

## Coulomb's law

Dielectric constant, definition of charge

Electricity

$F={kq_{1}q_{2} \over r_{2}}$ The force resulting from two nearby charges is equal to k times charge one times charge two divided by the square of the distance between the charges.

$E={F \over q}$ The electric field created by a charge is equal to the force generated divided by the charge.

$E={kq \over r_{2}}$ Electric field is equal to a constant, “k”, times the charge divided by the square of the distance between the charge and the point in question.

$U={(kq_{1}q_{2}) \over r}$ Electric potential energy is equal to a constant, “k” multiplied by the two charges and divided by the distance between the charges.

Variables

F: Force (N) k: a constant, 99 (N•m2/C2) q1: charge one (C) q2: charge two (C) r: distance between the two charges, (m)

A charge in an electrical field feels a force. The charge is not a vector, but force is a vector, and so is the electric field. If a charge is positive, then force and the electric field point in the same direction. If the charge is negative, then the electric field and force vectors point in opposite directions.

A point charge in space causes an electric field. The field is stronger closer to the point and weaker farther away.

## Ampere's law

Definition of current, magnetic permittivity