Electric Charges & Fields – Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering the fundamental concepts, constants, laws, and methods related to electric charges and fields as presented in the lecture notes.

Electric Charge

An intrinsic property of elementary particles that causes them to experience electromagnetic interaction; a scalar quantity measured in coulombs (C).

Coulomb (C)

The SI unit of electric charge; equal to the charge transported by a current of 1 ampere in 1 second.

Elementary Charge (e)

The magnitude of the charge of a single proton (+1.6 × 10⁻¹⁹ C) or electron (−1.6 × 10⁻¹⁹ C).

Electron

Negatively charged particle with charge −1.6 × 10⁻¹⁹ C and mass 9.1 × 10⁻³¹ kg.

Proton

Positively charged particle with charge +1.6 × 10⁻¹⁹ C and mass 1.67 × 10⁻²⁷ kg.

Neutron

Electrically neutral particle with mass roughly equal to that of a proton; charge 0 C.

Conservation of Charge

Total charge in an isolated system remains constant; charge can neither be created nor destroyed, only transferred.

Quantization of Charge

Charge exists in discrete integral multiples of the elementary charge: q = n e, where n is an integer.

Point Charge

A charged body whose size is negligible compared with the distance to other charges, allowing it to be treated as a single point.

Electrostatic Force

The force between stationary electric charges; described by Coulomb’s law.

Coulomb’s Law

Magnitude of the force between two point charges: F = k |q₁q₂| / r², directed along the line joining the charges.

Coulomb’s Constant (k)

Proportionality constant in Coulomb’s law; k = 9 × 10⁹ N·m²/C² in vacuum.

Permittivity of Free Space (ε₀)

A physical constant describing the ability of vacuum to permit electric field lines; ε₀ = 8.85 × 10⁻¹² C²/N·m².

Relative Permittivity (Dielectric Constant)

Ratio ε_r = ε / ε₀; indicates how a medium reduces the electric force compared with vacuum.

Central Force

A force that acts along the line joining two bodies; electrostatic force is central.

Inverse Square Law

Principle that a quantity (e.g., electrostatic force) varies as 1/r² with distance r from the source.

Long-Range Force

A force whose influence extends over large distances without significant attenuation; Coulomb force is long-range.

Specific Charge

Ratio of charge to mass (q/m) for a particle or body.

Charging by Friction

Transfer of electrons between two objects when rubbed together, leaving one positively and the other negatively charged.

Charging by Conduction

Process of charging a conductor by direct contact with another charged body, allowing electron flow.

Charging by Induction

Charging a body without contact by rearranging its charges in the presence of a nearby charged object.

Earthing (Grounding)

Connecting a charged object to Earth to allow excess charge to flow away, neutralising the object.

Conductor

Material with abundant free electrons allowing easy charge flow; can be charged by conduction.

Semiconductor

Material with moderate electrical conductivity; charge carriers include electrons and holes.

Insulator

Material with negligible free electrons; charges do not flow easily but can be charged by friction or induction.

Addition of Charges

Total charge of a system equals the algebraic sum of individual charges: Q_total = q₁ + q₂ + q₃ + …

Vector Form of Coulomb’s Law

𝐅₁₂ = k q₁q₂ (𝐫₁₂ / |𝐫₁₂|³), indicating magnitude and direction of the force between charges and satisfying Newton’s 3rd law.

Electrons per Coulomb

Approximately 6.25 × 10¹⁸ electrons constitute 1 C of charge.

Mass Change on Charging

A neutral body gains mass when it acquires electrons (negative charging) and loses mass when electrons are removed (positive charging).

Accelerated Charge Radiation

An accelerating electric charge emits electromagnetic energy as radiation.