Electric Charges, Fields, and Dipoles Flashcards

Flashcard deck covering the principle of superposition, equilibrium of charges, electric field intensity, continuous charge distributions, electric lines of force, and electric dipole properties based on the ISC Physics transcript.

Principle of Superposition for Electric Forces

The principle stating that if a system contains a number of interacting charges, the net force on any one charge due to the other charges is the vector sum of all individual forces exerted on it by all the other charges, calculated independently using Coulomb's law.

Translational Equilibrium of a Charge

The state of a charge or system of charges where the net electrostatic force acting on each charge composing the system is equal to zero ($\vec{F}_{\text{net}} = 0$).

Stable Equilibrium

An equilibrium state where a slight displacement of any charge produces restoring forces that act to return the system to its original state.

Unstable Equilibrium

An equilibrium state where a slight disturbance causes the system to deviate further away from its original position.

Neutral Equilibrium

An equilibrium state where a small displacement of a charge produces no restoring forces and does not further disturb the system.

Electric Field

The space surrounding an electric charge $q$ in which another charge $q_0$ experiences an electrostatic force of attraction or repulsion.

Source-Charge

The electric charge, group of point-charges, or continuous distribution of charges that creates an electric field in surrounding space.

Test-Charge

A conceptual, vanishingly small positive point-charge ($q_0 \rightarrow 0$) used to test and analyze electric fields without disturbing the field set up by the source-charge.

Electric Field Intensity

The force experienced per unit positive test-charge placed at a given point in an electric field, given by $\vec{E} = \lim_{q_0 \to 0} \frac{\vec{F}}{q_0}$ with SI units of $N\,C^{-1}$ or $V\,m^{-1}$.

Linear Charge Density

The quantity of electric charge per unit length along a continuous line charge distribution, represented by $\lambda = \frac{dq}{dl}$.

Surface Charge Density

The quantity of electric charge per unit area over a continuous surface charge distribution, represented by $\sigma = \frac{dq}{dS}$.

Volume Charge Density

The quantity of electric charge per unit volume throughout a continuous volume charge distribution, represented by $\rho = \frac{dq}{dV}$.

Electric Line of Force

An imaginary smooth curve drawn in an electric field along which a free, isolated positive charge moves, such that the tangent at any point gives the direction of the electric field at that point.

Neutral Point

A location in an electric field created by equal and similar charges where the electric field from one charge is equal and opposite to that from the other, resulting in a net field of zero.

Electric Dipole

A system consisting of a pair of equal and opposite point-charges separated by a small distance.

Electric Dipole Moment

A vector quantity ($\vec{p}$) equal to the product of one charge magnitude and the distance between the two charges ($p = q \times 2l$), pointing from the negative charge to the positive charge.

Debye

A unit used to measure electric dipole moment, where $1\,\text{debye} = 3.336 \times 10^{-30}\,C\,m$.

Axial Position (End-on Position)

A position along the extended axis of an electric dipole where the magnitude of the electric field intensity for a short dipole ($r \gg l$) is given by $E_a = \frac{1}{4\pi\varepsilon_0} \frac{2 p}{r^3}$.