Electric Forces and Fields Glossary

A material with free charges that can move throughout the volume. In electrostatic equilibrium, the internal field is zero and excess charge resides on the surface.

The law stating that the electrostatic force between two point charges is proportional to the product of the charges and inversely proportional to the square of the distance between them.

A pair of equal and opposite charges $+q$ and $-q$ separated by a distance $d$. The dipole moment is $p = qd$, pointing from $-q$ to $+q$.

A vector field giving the force per unit positive charge at each point in space. Units: N/C or V/m.

The surface integral of the electric field over a surface: $\Phi_E = \oint \vec{E} \cdot d\vec{A}$. It measures the 'flow' of field lines through the surface.

The electric potential energy per unit charge at a point in space. A scalar quantity measured in volts (V = J/C).

A unit of energy equal to the work done on an electron accelerated through 1 V of potential difference: $1 \text{ eV} = 1.6 \times 10^{-19}$ J.

A surface on which all points are at the same electric potential. The electric field is always perpendicular to equipotential surfaces.

A fundamental law relating the electric flux through a closed surface to the total charge enclosed: $\Phi_E = Q_{\text{enc}}/\epsilon_0$.

A material in which charges are bound and cannot move freely. An external field polarizes the molecules but does not create a current.

The constant $\epsilon_0 = 8.85 \times 10^{-12}$ C$^2$/(N m$^2$) that appears in Coulomb's law and Gauss's law. Related to Coulomb's constant by $k = 1/(4\pi\epsilon_0)$.

The difference in electric potential between two points: $\Delta V = V_B - V_A$. It equals the work done per unit charge in moving a charge between those points.

The net field or force from multiple charges is the vector sum of the individual contributions from each charge.