Electric Fields and Conductors - Vocabulary

Key vocabulary terms from the lecture notes on insulators, conductors, dipoles, electric fields, field lines, and related concepts.

Insulator

A material in which electrons are tightly bound to nuclei and are not free to move; charging leaves immobile patches of ions on the surface.

Conductor

A material (e.g., metals) where outer (valence) electrons are weakly bound and wander through the solid, forming a mobile sea of electrons.

Valence electrons

Outer electrons that are weakly bound and free to move in metals.

Sea of electrons

Delocalized electrons in a metal that move throughout the solid, enabling high electrical conductivity.

Electric dipole

Two equal but opposite charges separated by a distance; total net charge is zero.

Permanent electric dipole

A dipole arising from an asymmetry in charge distribution that gives a constant dipole moment.

Water (H2O) as a permanent dipole

Water molecules have partial positive charges on hydrogens and partial negative charge on oxygen due to unequal sharing of electrons.

Hydrogen bond

A weak dipole attraction between a hydrogen atom of one molecule and a negatively charged atom (like oxygen) in another molecule.

Electric field

A region around charges where other charges experience force; an influence that fills space and can be represented by field lines.

Coulomb’s law

The force between two point charges q1 and q2 is F = k q1 q2 / r^2; the field E1 from a charge q1 at distance r is the force per unit charge.

Electric field vector

A vector that represents the magnitude and direction of the electric field at a point; tangent to the electric field lines.

Electric field line

A curve whose tangent at any point gives the direction of the electric field; lines start on positive charges and end on negative charges and never cross.

Uniform electric field

An electric field with the same magnitude and direction at all points in a region, such as between ideal parallel plates.

Permittivity (epsilon0)

A constant (≈8.85×10^-12 C^2/(N·m^2)) relating electric field and charge density; E = σ/ε0 for a parallel-plate arrangement.

Electric field inside a conductor (electrostatic equilibrium)

Zero; charges move until any interior field cancels, localizing excess charge on the surface.

Surface charge

Excess charge that resides on the surface of a conductor; interior charges would create a field, so charges move to the surface.

Field lines perpendicular to conducting surfaces

The electric field at a conductor’s surface is perpendicular to the surface; any tangential component would move surface charges.

Field concentration at sharp points

Charge density and thus the electric field are higher at sharp points on a conductor.

Electric dipole moment

A vector pointing from the negative to the positive charge of a dipole, indicating its orientation and strength.

Torque on a dipole in a uniform electric field

A uniform field exerts a torque on a dipole, causing it to rotate until the dipole moment aligns with the field.

Equilibrium orientation of a dipole

The position where the electric dipole moment is aligned with the electric field, producing no net rotational torque.

Superposition of electric fields

The net electric field is the vector sum of the individual fields from all charges.