Chapter One – Electric Charges and Fields (Vocabulary Flashcards)

40 vocabulary flashcards summarising key terms and definitions from Chapter One: Electric Charges and Fields, covering charge properties, laws, field concepts and applications.

Static Electricity

Electric charge that remains at rest on an object; produced by rubbing or friction

Electrostatics

Branch of physics dealing with forces, fields and potentials arising from static electric charges

Electric Charge

A fundamental property of matter causing it to experience a force in an electric field; comes in positive and negative forms

Polarity of Charge

The characteristic that differentiates positive and negative charges; like polarities repel, unlike polarities attract

Conductors

Materials (e.g., metals, human body) in which electric charges are free to move easily

Insulators

Materials (e.g., glass, plastic) that resist the free movement of electric charge

Semiconductors

Materials whose electrical conductivity lies between conductors and insulators

Additivity of Charge

Property that the total charge of a system equals the algebraic sum of individual charges

Conservation of Charge

Principle stating that total electric charge of an isolated system remains constant

Quantisation of Charge

Fact that charge exists only in integral multiples of the elementary charge e (≈1.6×10⁻¹⁹ C)

Coulomb’s Law

Force between two point charges is proportional to the product of their charges and inversely proportional to the square of their separation

Permittivity of Free Space (ε₀)

Constant (8.854×10⁻¹² C² N⁻¹ m⁻²) appearing in Coulomb’s law and Gauss’s law

Principle of Superposition

Net electric force (or field) on a charge equals the vector sum of forces (or fields) from all other charges

Point Charge

An idealised charge whose size is negligible compared with distances of interest

Electric Field (E)

Vector field defined as the force per unit positive test charge at each point in space

Source Charge

Charge that creates an electric field

Test Charge

Hypothetical small positive charge used to probe an electric field without disturbing it

Electric Field Lines

Imaginary curves whose tangents give the direction of E and density indicates its magnitude

Electric Flux (Φ)

Measure of the number of electric field lines passing through a surface; Φ = E·ΔS

Gaussian Surface

Closed imaginary surface used with Gauss’s law to calculate electric field

Gauss’s Law

Total electric flux through a closed surface equals enclosed charge divided by ε₀ (Φ = q_enc/ε₀)

Electric Dipole

Pair of equal and opposite charges separated by a small distance

Dipole Moment (p)

Vector quantity p = q × 2a directed from negative to positive charge; measures dipole strength

Torque on a Dipole

Rotational effect τ = p × E experienced by a dipole in a uniform electric field

Linear Charge Density (λ)

Charge per unit length (C m⁻¹) along a line or wire

Surface Charge Density (σ)

Charge per unit area (C m⁻²) on a surface

Volume Charge Density (ρ)

Charge per unit volume (C m⁻³) within a region

Inverse-Square Law

Dependence of force or field magnitude varying as 1/r² with distance

Permittivity (General)

Material property describing how an electric field affects and is affected by a medium

Electric Field of a Line Charge

E = λ/(2π ε₀ r) radially outward (or inward) from a long straight uniform wire

Electric Field of an Infinite Plane Sheet

E = σ/(2 ε₀) normal to the sheet, independent of distance

Electric Field inside a Conductor

Zero in electrostatic equilibrium; charges reside on the surface

Electroscope

Device (e.g., gold-leaf electroscope) used to detect and compare electric charges

Point Dipole

Limit of a dipole where separation →0 but dipole moment p remains finite

Field of a Dipole on Axis

E = (1/4π ε₀)(2p/r³) along the dipole axis (for r >> separation)

Field of a Dipole on Equatorial Plane

E = (1/4π ε₀)(p/r³) opposite to dipole moment direction (for r >> separation)

Unit Vector (î, ĵ, k̂)

Vector of unit magnitude indicating direction along coordinate axes

Elementary Charge (e)

Smallest free charge magnitude ≈1.602×10⁻¹⁹ C, carried by a proton (+e) or electron (–e)

Charge Density Distribution

Continuous model (λ, σ, ρ) for describing large collections of charges