Electrostatics – Vocabulary Review

26 vocabulary flashcards covering fundamental concepts from the electrostatics lecture notes, including charge, electric forces, fields, dipoles, and methods of charging.

Insulator

A material in which electric charges do not move freely; electrons are tightly bound to their atoms (e.g., rubber, glass).

Conductor

A material that allows electric charges to move freely through it because of loosely bound outer electrons (e.g., metals).

Elementary charge (e)

The magnitude of the charge of a single proton (or the negative of an electron): 1.60 × 10⁻¹⁹ C.

Charging by friction

Process in which two insulators are rubbed together, transferring electrons and leaving one object positively charged and the other negatively charged.

Charging by conduction (contact)

Charging a conductor by touching it with a charged object, allowing electrons to flow until both objects share charge.

Charging by polarization

Temporary separation of charges within an insulator when placed near a charged object; no net charge is transferred.

Charging by induction

Charging a conductor without contact by bringing a charged object near it and grounding the conductor, leaving it with opposite charge.

Coulomb’s law

The electric force between two point charges is F = k |q₁q₂| / r², directed along the line joining them.

Coulomb’s constant (k)

Proportionality constant in Coulomb’s law: k ≈ 8.99 × 10⁹ N·m²/C² (k = 1/4πϵ₀).

Permittivity of free space (ϵ₀)

A physical constant describing how electric fields interact with vacuum: ϵ₀ ≈ 8.85 × 10⁻¹² C²/(N·m²).

Electric force (F)

The force exerted on a charge by other charges; F = qE for a charge q in an electric field E.

Electric field (E)

Region of space where an electric charge experiences a force; defined as E = F/q and for a point charge E = k q / r².

Principle of superposition

The net electric field or force is the vector sum of fields or forces produced by each charge separately.

Electric field lines

Imaginary lines indicating direction and magnitude of E; tangent gives direction, density gives strength, lines start on + and end on – charges.

Electric dipole

A pair of equal and opposite point charges separated by a small distance d.

Dipole moment (p)

Vector quantity p = q d directed from negative to positive charge; measures strength of a dipole (units: C·m).

Torque on a dipole

A dipole in uniform E experiences τ = p E sin θ, tending to align p with the field.

Potential energy of a dipole

U = –p E cos θ; minimum when p is parallel to E (θ = 0°) and maximum when antiparallel (θ = 180°).

Millikan oil-drop experiment

Experiment that measured the elementary charge by balancing gravitational and electric forces on charged oil drops.

Quantization of charge

Electric charge exists only in integer multiples of the elementary charge: Q = n e, where n is an integer.

Surface charge density (σ)

Charge per unit area on a surface (C/m²).

Linear charge density (λ)

Charge per unit length along a line or wire (C/m).

Volume charge density (ρ)

Charge per unit volume within a region (C/m³).

Uniform electric field

A field with constant magnitude and direction, such as between two large parallel plates; E = V/d.

Work done by an electric field

W = –ΔU = q ΔV for moving charge q through potential difference ΔV; equals change in potential energy.

Acceleration in an electric field

A charged particle of mass m and charge q in uniform E experiences acceleration a = qE / m.