Physics Chapter 16 – Electric Charge and Electric Field

Vocabulary flashcards covering fundamental terms and definitions from Chapter 16: Electric Charge and Electric Field.

Electric Charge

A fundamental property of matter that comes in two types, positive and negative, and gives rise to electric forces.

Static Electricity

Electric phenomena associated with stationary charges, often produced by rubbing materials together.

Conservation of Charge

Physical law stating that the algebraic sum of all electric charges in any closed system remains constant.

Quantization of Charge

The fact that electric charge exists only in integer multiples of the elementary charge e = 1.602 × 10⁻¹⁹ C.

Electron

A negatively charged sub-atomic particle found in the electron cloud around an atom’s nucleus.

Proton

A positively charged particle located in an atom’s nucleus; carries charge +e.

Neutron

Electrically neutral particle in the atomic nucleus with approximately the same mass as a proton.

Ionization

Process of removing an electron from an atom, producing a charged ion.

Positive Ion (Cation)

An atom or molecule that has lost one or more electrons, giving it a net positive charge.

Negative Ion (Anion)

An atom or molecule that has gained one or more electrons, giving it a net negative charge.

Polar Molecule

A neutral molecule with an uneven distribution of charge, forming a permanent electric dipole (e.g., water).

Conductor

Material, typically a metal, in which electric charge flows freely due to loosely bound electrons.

Insulator

Material in which electric charge does not flow easily; also called a non-conductor.

Semiconductor

Material whose conductivity lies between that of conductors and insulators and can be altered by doping.

Charging by Conduction

Transferring charge to an object through direct physical contact with a charged body.

Charging by Induction

Producing charge separation in, and charging of, a conductor without contact, using a nearby charged object.

Electroscope

Instrument that detects the presence and sign of electric charge via the motion of metal leaves.

Coulomb’s Law

F = k |Q₁Q₂| / r²; the electric force between two point charges is proportional to the product of their charges and inversely proportional to the square of their separation.

Coulomb (C)

SI unit of electric charge; the amount of charge that passes in 1 s with a current of 1 A.

Permittivity of Free Space (ε₀)

Physical constant (8.85 × 10⁻¹² C²/N·m²) relating electric field and electric flux in vacuum.

Proportionality Constant k

k = 1 / (4π ε₀) ≈ 8.99 × 10⁹ N·m²/C² in Coulomb’s law.

Microcoulomb (µC)

A sub-multiple of the coulomb; 1 µC = 10⁻⁶ C.

Electric Field (E)

Force per unit positive test charge; E = F/q.

Electric Field of a Point Charge

E = k Q / r² directed radially away from a positive charge and toward a negative charge.

Superposition Principle (Electric Fields)

Net electric field equals the vector sum of individual fields produced by each charge.

Electric Field Lines

Imaginary lines that indicate the direction and relative strength of an electric field; originate on + charges and terminate on – charges.

Electric Dipole

Two equal and opposite point charges separated by a small distance.

Parallel-Plate Capacitor

Device consisting of two closely spaced, oppositely charged conducting plates that produce a uniform electric field between them.

Electrostatic Equilibrium

State in a conductor where charges are at rest and the internal electric field is zero.

Screening (Faraday Cage)

Exclusion of external electric fields from a region enclosed by a conducting shell.

Electric Flux (Φ_E)

Measure of the number of electric field lines passing through a surface; Φ_E = Σ E·ΔA cosθ.

Gauss’s Law

The net electric flux through a closed surface equals the enclosed charge divided by ε₀; ΦE = Qencl / ε₀.

Point Charge

Idealized model of a charged object whose size is negligible compared with distances of interest.

Vector Addition (Tail-to-Tip)

Graphical method to find the resultant of multiple vector quantities such as electric forces.

Electric Dipole Moment

Vector quantity p = q d directed from the negative to the positive charge of a dipole.

Polarization (Insulators)

Small displacement of bound charges in an insulator when exposed to an external electric field.

Lightning Rod

Sharp-pointed conductor that prevents lightning strikes by discharging accumulated charge into the air.

DNA Double Helix

Structure of DNA consisting of two antiparallel strands wound around each other and stabilized by electrostatic attractions between nucleotide bases.

Base Pairing (A-T and G-C)

Selective electrostatic attraction between adenine-thymine and guanine-cytosine bases in DNA replication.

Photocopy Machine Drum

Positively charged rotating cylinder that holds the latent electrostatic image attracting toner in a copier.

Laser Printer

Electrostatic printing device in which a computer-controlled laser writes an image on a charged drum to attract toner.