Electrostatics Lecture Flashcards

Vocabulary flashcards generated from electrostatics lecture notes covering core concepts, formulas, and theorems.

Electric Charge

A fundamental property of matter (just like mass), measured in Coulomb's ($\text{C}$), which is quantised as an integer multiple of $1.6 \times 10^{-19}\,\text{C}$.

Coulomb's Law

States that the force of interaction between any two charges is directly proportional to the product of charges and inversely proportional to the square of distance between them ($F = \frac{K q_1 q_2}{r^2}$).

Electric Field Intensity

The electrostatic field at any point of space defined as the force per unit charge ($\vec{E} = \frac{\vec{F}}{q}$), expressed in units of $\text{N}\cdot\text{C}^{-1}$.

Superposition Principle

States that the force of interaction between any two point charges is independent of the presence or absence of any other charge in the universe.

Electric Field Lines

A visual representation of the electric field whose density is proportional to the magnitude of the field and whose tangent gives the direction of the field.

Electric Dipole Moment

A vector directed from the negative charge to the positive charge with magnitude $\vec{p} = 2 q a$, where two equal and opposite charges are separated by a small distance $2 a$.

Point Dipole

A mathematical idealisation where the separation between dipole charges is taken as arbitrarily close to zero ($r \gg a$).

Electrostatic Potential

The negative of work done by electrostatic forces in bringing a unit charge from infinity to a given point.

Equipotential Surface

A surface which joins points having the same potential, and is always perpendicular to electric field lines.

Electrostatic Potential Energy

For a system of particles, the negative of work done by the electric field in bringing all the particles from infinity to the given configuration.

Area Vector

For any small surface having surface area $d S$, a vector whose magnitude is equal to $d S$ and whose direction is perpendicular to $d S$.

Electric Flux

The total electric field measure associated with a surface area patch, defined mathematically as $d\phi = \vec{E} \cdot d\vec{S}$.

Gauss's Law

States that the net flux associated with any closed surface is equal to the charge enclosed divided by $\epsilon_0$ ($\phi = \oint \vec{E} \cdot d\vec{S} = \frac{q_{\text{enclosed}}}{\epsilon_0}$).

Shell Theorem 1

States that for an outside point, a uniformly charged thin shell behaves as if all the charge were concentrated at its centre.

Shell Theorem 2

States that for an inside point, a uniformly charged thin spherical shell behaves as if there is no charge enclosed.

Self-Energy

The negative of work done by electrostatic forces in assembling an electrostatic system.