Electrostatic Potential and Capacitance Practice Flashcards

These vocabulary flashcards cover the fundamental definitions, formulas, and concepts of electrostatic potential, capacitance, and the behavior of conductors and dielectrics in an electric field as described in the lecture notes.

Conservative Forces

Forces where the work done in moving a body between two points depends only on the initial and final positions and is independent of the path taken, such as spring force, gravitational force, and Coulomb force.

Electrostatic Potential Energy Difference ($U_P - U_R$)

The work required to be done by an external force in moving (without accelerating) a charge $q$ from one point to another in the electric field of an arbitrary charge configuration.

Electrostatic Potential ($V$)

The work done per unit test charge in bringing a unit positive charge from infinity to a specific point without acceleration.

Electron Volt ($eV$)

A unit of energy equal to the energy gained by an electron ($q = e = 1.6 \times 10^{-19} \text{\,C}$) when accelerated by a potential difference of $1 \text{\,volt}$, equivalent to $1.6 \times 10^{-19} \text{\,J}$.

Equipotential Surface

A surface that has a constant value of potential at all points, requiring no work to move a test charge along its surface and always remaining normal to the electric field.

Capacitance ($C$)

A constant defined as the ratio of the charge $Q$ on a conductor to the potential difference $V$ between conductors, given by the formula $C = Q/V$. Its SI unit is the farad ($F$).

Dielectric Strength

The maximum electric field that a dielectric medium can withstand without the breakdown of its insulating properties; for air, it is approximately $3 \times 10^6 \text{\,V\,m}^{-1}$.

Dielectric Constant ($K$)

The dimensionless ratio of the permittivity of a substance to the permittivity of a vacuum ($\frac{\epsilon}{\epsilon_0}$), representing the factor by which capacitance increases when the dielectric fully occupies the space between capacitor plates.

Polarisation ($\text{P}$)

The dipole moment per unit volume of a dielectric material, which for linear isotropic dielectrics is related to the electric field by the formula \text{P} = \text{\epsilon}_0 \text{\chi}_e \text{E}, where \text{\chi}_e is the electric susceptibility.

Energy Density of Electric Field ($u$)

The energy stored per unit volume in a region with an electric field, defined by the expression u = \frac{1}{2} \text{\epsilon}_0 \text{E}^2.

Electrostatic Shielding

A phenomenon where the electric field inside a cavity within a conductor is zero, regardless of external charges or fields, protecting sensitive instruments from electrical influence.

Non-polar Molecule

A molecule where the centers of positive and negative charges coincide, resulting in no permanent dipole moment, such as in oxygen ($\text{O}_2$) or hydrogen ($\text{H}_2$).

Polar Molecule

A molecule where the centers of positive and negative charges are separated even in the absence of an external field, giving it a permanent dipole moment, such as $\text{HCl}$ or $\text{H}_2\text{O}$.

Electric Field at the Surface of a Charged Conductor

The field is normal to the surface and its magnitude is given by \text{E} = \frac{\text{\sigma}}{\text{\epsilon}_0} \text{\mathbf{\hat{n}}}, where \text{\sigma} is the surface charge density and \text{\mathbf{\hat{n}}} is the unit vector normal to the surface.

Series Combination of Capacitors

An arrangement where capacitors are connected such that they all carry the same charge $Q$, and the effective capacitance $C$ is found using $\frac{1}{C} = \frac{1}{C_1} + \frac{1}{C_2} + \text{...} + \frac{1}{C_n}$.

Parallel Combination of Capacitors

An arrangement where capacitors are connected such that the potential difference $V$ across each is the same, and the effective capacitance $C$ is the sum of individual capacitances: $C = C_1 + C_2 + \text{...} + C_n$.