Electric Charges and Field

Comprehensive vocabulary flashcards covering the fundamental concepts of electrostatics, including electric charges, forces, fields, dipoles, and Gauss's theorem based on the lecture transcript.

Frictional Electricity

The electricity developed by rubbing or friction, often referred to as static electricity.

Elektron

The Greek name for amber, which is the historical origin of terms such as electricity, electric force, and electron.

Electromagnetism

The unified study of electricity and magnetism, as both phenomena can be derived from charged particles in motion.

Electric Charge

An intrinsic property of elementary particles, such as electrons and protons, which gives rise to electric force between objects.

Coulomb ($C$)

The SI unit of electric charge.

Electrostatics

The study of electric charges at rest, including the forces, fields, and potentials associated with static charges.

Fundamental Law of Electrostatics

The principle stating that like charges repel and unlike charges attract each other.

Polarity of Charge

The property that distinguishes the two kinds of electric charges: positive and negative.

Work Function

The energy required to remove an electron from the surface of a material; in frictional electricity, electrons move from the material with the lower value to the one with the higher value.

Conductors

Substances through which electric charges can flow easily because they contain a large number of free electrons.

Insulators

Substances through which electric charges cannot flow easily because electrons are tightly bound to the nucleus.

Grounding (Earthing)

The process in which a body shares its charges with the earth through a connecting conductor.

Electrostatic Induction

The phenomenon of temporary electrification of a conductor where opposite charges appear at the closer end and similar charges appear at the farther end in the presence of a nearby charged body.

Gold-leaf Electroscope

A device used for detecting an electric charge and identifying its polarity based on the divergence of two thin gold leaves.

Additivity of Electric Charge

The property that the total charge of a system is the algebraic sum of all individual charges located at different points inside the system.

Quantization of Electric Charge

The principle that the total charge ($q$) of a body is always an integral multiple of a basic quantum of charge ($e$), expressed as $q = ne$.

Conservation of Charge

The law stating that the total charge of an isolated system remains constant; charges can neither be created nor destroyed, only transferred.

Coulomb's Law

States that the force of attraction or repulsion between two stationary point charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them.

Electrostatic Force Constant ($k$)

The proportionality constant in Coulomb's law, approximately equal to $9 \times 10^9\,Nm^2C^{-2}$ in free space.

Permittivity ($\epsilon$)

A property of the medium which determines the electric force between two charges situated in that medium.

Dielectric Constant ($K$)

Also called relative permittivity ($\epsilon_r$), it is the ratio of the force between two charges in free space to the force between them in a given medium.

Principle of Superposition (Electrostatic Forces)

States that when a number of charges are interacting, the total force on a given charge is the vector sum of the forces exerted on it due to all other charges.

Electric Field ($E$)

Defined as the electrostatic force per unit test charge acting on a vanishingly small positive test charge placed at a point, measured in $NC^{-1}$ or $Vm^{-1}$.

Spherically Symmetric (Radial) Field

An electric field, such as that produced by a point charge, where the magnitude of $E$ depends only on the distance from the charge and not the direction.

Linear Charge Density ($\lambda$)

The charge per unit length of a line charge distribution, expressed in $Cm^{-1}$.

Surface Charge Density ($\sigma$)

The charge per unit area of a surface charge distribution, expressed in $Cm^{-2}$.

Volume Charge Density ($\rho$)

The charge per unit volume of a volume charge distribution, expressed in $Cm^{-3}$.

Electric Dipole

A pair of equal and opposite charges separated by a small distance ($2a$).

Electric Dipole Moment ($p$)

A vector quantity measuring dipole strength, calculated as $p = q \times 2a$, directed from the negative to the positive charge.

Electric Line of Force

An imaginary curve along which a small positive charge would move; the tangent to the curve at any point indicates the direction of the electric field.

Electric Flux ($\Phi_{E}$)

The total number of electric lines of force passing normally through a given area, calculated as the surface integral of the electric field.

Gauss's Theorem

States that the total electric flux through a closed surface is $1/\epsilon_0$ times the net charge enclosed by that surface.

Gaussian Surface

Any hypothetical closed surface enclosing a charge used to evaluate the surface integral of the electric field.