Electric Charges and Fields Practice Flashcards

Vocabulary practice flashcards covering introductory electrostatics, charge properties, Coulomb's law, electric fields, dipoles, and Gauss's law from Chapter 1 notes.

Static

Anything that does not move or change with time.

Electrostatics

The study of forces, fields, and potentials arising from static charges.

Thales of Miletus

The Greek scientist from 600 BC who is credited with discovering that amber rubbed with wool or silk cloth attracts light objects.

Elektron

The Greek word for amber, from which the name electricity is coined.

Polarity of charge

The property which differentiates the two kinds of charges (positive and negative).

Benjamin Franklin

The American scientist who named the two types of charges as positive and negative.

Conductors

Substances that allow the passage of electricity through them, such as metals, human and animal bodies, and the earth.

Insulators

Substances that offer high resistance to the passage of electricity, such as glass, porcelain, plastic, nylon, and wood.

Gold Leaf Electroscope

A simple apparatus used to detect charge on a body, consisting of a vertical metal rod with two thin gold leaves at the bottom.

Additivity of charge

The principle that the total charge of a system is the algebraic sum of individual charges: $q = q_1 + q_2 + q_3 + ... + q_n$.

Conservation of charge

The principle stating that the total charge of an isolated system remains constant, and net charge cannot be created or destroyed.

Quantization of charge

The principle that the charge of a body is always an integral multiple of a basic electronic charge: $q = \text{±} ne$.

Electronic charge ($e$)

The basic unit of charge, equal to $1.602 \times 10^{-19} \text{ C}$.

Coulomb’s Law

States that the force between two stationary charges is directly proportional to the product of charges and inversely proportional to the square of the distance: $F = \frac{1}{4\text{π}\text{ε}_0} \frac{q_1q_2}{r^2}$.

Superposition Principle

The force on a charge due to a number of other charges is the vector sum of forces due to those individual charges.

Electric Field

The region around a charge where its effect can be felt, defined as the force per unit charge: $E = \frac{F}{q}$.

Electric Field Lines

A curve drawn such that the tangent to it at any point is in the direction of the net electric field at that point.

Electric Flux ($\text{ϕ}$)

The measure of the flow of the electric field through a surface, given by \text{ϕ} = \text{∫} E \text{ dS} \text{ cos}(\text{θ}).

Electric Dipole

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

Electric Dipole Moment ($p$)

A vector quantity representing a dipole, defined for charges $q$ and separation $2a$ as $p = 2qa$.

Axial Field of a Dipole

The electric field at a point along the axis of the dipole, expressed as $E = \frac{1}{4\text{π}\text{ε}_0} \frac{2p}{r^3}$ for $r \text{ ≫ } a$.

Equatorial Field of a Dipole

The electric field at a point on the equatorial line of the dipole, expressed as $E = \frac{1}{4\text{π}\text{ε}_0} \frac{p}{r^3}$ for $r \text{ ≫ } a$.

Torque ($\text{τ}$)

The turning effect on a dipole in a uniform external field, given by $\text{τ} = pE \text{ sin}(\text{θ})$ or $\text{τ} = \text{→}{p} \text{ × } \text{→}{E}$.

Linear Charge Density ($\text{λ}$)

The charge per unit length of a wire, given by $\text{λ} = \frac{q}{l}$ with units $\text{C/m}$.

Surface Charge Density ($\text{σ}$)

The charge per unit area of a surface, given by $\text{σ} = \frac{q}{S}$ with units $\text{C/m}^2$.

Volume Charge Density ($\text{ρ}$)

The charge per unit volume, given by $\text{ρ} = \frac{q}{V}$ with units $\text{C/m}^3$.

Gauss’s Law

States that the total electric flux through a closed surface is equal to $\frac{1}{\text{ε}_0}$ times the total charge enclosed: $\text{ϕ} = \frac{q}{\text{ε}_0}$.

Gaussian Surface

The closed surface over which the electric flux is calculated using Gauss's law.