General Physics II: Electricity, Oscillations, and Waves

Comprehensive practice flashcards defining foundational vocabulary, concepts, formulas, and phenomena across electrostatics, conductors, dielectrics, direct current, electromagnetism, oscillations, and wave mechanics based on General Physics Volume II.

Elementary charge ($e$)

The smallest known charge in nature, with a magnitude of $e = 1.6 \times 10^{-19}\,\text{C}$, carried by protons ($+e$ with mass $1.67 \times 10^{-27}\,\text{kg}$) and electrons ($-e$ with mass $9.1 \times 10^{-31}\,\text{kg}$).

Electric dipole moment ($\mathbf{p}_e$)

A vector defined as $\mathbf{p}_e = q\mathbf{l}$, where $\mathbf{l}$ is the vector directed from the negative charge $-q$ to the positive charge $+q$ with length equal to the separation distance $l$, characterizing the electrical properties of an electric dipole.

Electric displacement vector ($\mathbf{D}$)

A physical vector quantity used to describe the electric field independently of the medium's properties, defined in a homogeneous and isotropic medium as $\mathbf{D} = \varepsilon_0 \varepsilon \mathbf{E}$, measured in coulombs per square meter ($\text{C/m}^2$).

Poisson's equation (Differential form of Gauss's law)

The differential form of Gauss's law expressing the relationship between the electric displacement vector and the volume charge density at a single point in an electric field: $\text{div}\mathbf{D} = \rho$.

Equipotential surface

The locus of all points in an electric field having the same electric potential ($V = \text{const}$), always perpendicular at every point to the electric field lines.

Electrostatic equilibrium conditions for a conductor

The electrostatic state in which the electric field inside the conductor must be zero ($\mathbf{E}_{\text{internal}} = 0$) and the tangential component of the electric field on the conductor surface must be zero ($E_t = 0$, so $\mathbf{E} = \mathbf{E}_n$).

Electrostatic shielding (Electric screen)

The phenomenon whereby a hollow conductor in electrostatic equilibrium acts as a protective shield for objects placed inside its cavity, because the electric field inside the cavity is strictly zero and external electric fields cannot affect it.

Point effect (Lightning rod effect)

The phenomenon in which electric charge strongly concentrates at sharp tips or points of a conductor, producing an intense localized electric field that ionizes surrounding air molecules, giving rise to an 'electric wind' and charge loss from the tip.

Capacitance of an isolated conductor ($C$)

A physical quantity numerically equal to the electric charge required to raise the electric potential of the conductor by one unit: $C = \frac{Q}{V}$, measured in farads ($\text{F}$).

Electric polarization vector ($\mathbf{P}_e$)

A vector quantity defined as the total electric dipole moment of all molecules contained within a unit volume of a dielectric: $\mathbf{P}_e = \frac{\sum \mathbf{p}_{e_i}}{\Delta V}$, measured in $\text{C/m}^2$.

Rochelle salt (Seignette salt)

A crystalline dielectric with formula $\text{NaK}(\text{C}_4\text{H}_4\text{O}_6) \cdot 4\text{H}_2\text{O}$ that exhibits an extraordinarily high dielectric constant (up to $10{,}000$), dielectric hysteresis, and loses its ferroelectric properties above a Curie temperature of approximately $25\,^{\circ}\text{C}$.

Current density vector ($\mathbf{j}$)

A vector at a point in a conducting medium pointing in the direction of motion of positive charge carriers, with magnitude equal to the current per unit cross-sectional area perpendicular to that motion: $j = \frac{dI}{dS_n} = n_0 |e| v$, measured in $\text{A/m}^2$.

Extraneous force (Non-electrostatic force)

A force of non-electrostatic nature inside a power source that acts against the electrostatic field to drive positive charges from regions of lower potential to regions of higher potential, maintaining a closed-circuit current.

Biot-Savart-Laplace law

A fundamental law stating that the magnetic induction $d\mathbf{B}$ produced by a current element $I\,d\mathbf{l}$ at distance $r$ is given by $d\mathbf{B} = \frac{\mu_0 \mu}{4\pi} \frac{I\,d\mathbf{l} \times \mathbf{r}}{r^3}$.

Magnetic field intensity vector ($\mathbf{H}$)

A vector characterizing the magnetic field generated purely by the electric current independently of the medium's magnetic properties, defined for a homogeneous isotropic medium as $\mathbf{H} = \frac{\mathbf{B}}{\mu_0 \mu}$, measured in $\text{A/m}$.

Ampère's circuital law

The theorem stating that the circulation (line integral) of the magnetic field intensity vector $\mathbf{H}$ along any closed curve $(C)$ equals the algebraic sum of the conduction currents threading the surface bounded by that curve: $\oint_{(C)} \mathbf{H}\cdot d\mathbf{l} = \sum_{i=1}^n I_i$.

Ampère force

The magnetic force exerted by a magnetic field $\mathbf{B}$ on a current element $I\,d\mathbf{l}$, defined by the vector cross product $d\mathbf{F} = I\,d\mathbf{l} \times \mathbf{B}$, with magnitude $dF = I\,dl\,B\sin(\alpha)$.

Lorentz force ($\mathbf{F}_L$)

The magnetic force exerted on a charged particle $q$ moving with velocity $\mathbf{v}$ in a magnetic field $\mathbf{B}$, given by $\mathbf{F}_L = q\mathbf{v} \times \mathbf{B}$, with magnitude $F_L = |q| v B \sin(\alpha)$.

Lenz's law

The general law stating that the induced current must always have such a direction that the magnetic field it produces opposes the change in magnetic flux that generated it.

Self-inductance ($L$)

A physical coefficient relating the self-induced magnetic flux through a circuit to the current flowing in that circuit (defined by $\Phi_m = LI$), measuring the electromagnetic inertia of the circuit and expressed in henrys ($\text{H}$).

Skin effect

The phenomenon in which high-frequency alternating currents tend to flow almost entirely along the outer surface layer of a conductor rather than uniformly through its interior, caused by internal self-induction.

Larmor angular velocity ($\omega_L$)

The angular velocity of the precession of an atomic electron's orbit around the direction of an external magnetic field $\mathbf{B}_0$, given by $\omega_L = \frac{e B_0}{2m}$.

Curie's law for paramagnetism

The empirical and theoretical law stating that the magnetic susceptibility of a paramagnetic substance is inversely proportional to its absolute temperature: $\chi_m = \frac{C}{T}$, where $C$ is the Curie constant.

Curie temperature ($T_c$)

The critical temperature above which a ferromagnetic material loses its spontaneous magnetization and remanence, transitioning completely into a paramagnetic substance (e.g., $770\,^{\circ}\text{C}$ for iron and $1127\,^{\circ}\text{C}$ for cobalt).

Ferrites

Ferromagnetic semiconductor compounds with general chemical formula $\text{MeO} \cdot \text{Fe}_2\text{O}_3$ (where $\text{Me}$ is a divalent metal) that possess high magnetic permeability combined with high electrical resistivity ($1$ to $10^7\,\Omega\cdot\text{m}$), eliminating energy loss from eddy currents at high frequencies.

Maxwell's First Hypothesis

The fundamental postulate stating that any magnetic field varying with time generates a vortex (rotational) electric field, quantitatively expressed by $\text{rot}\mathbf{E} = -\frac{\partial \mathbf{B}}{\partial t}$.

Displacement current

The concept introduced by Maxwell asserting that a time-varying electric field is equivalent to an electric current in its ability to produce a magnetic field, with displacement current density defined as $\mathbf{j}_d = \frac{\partial \mathbf{D}}{\partial t}$.

Umov-Poynting vector ($\mathbf{\wp}$)

The directional energy flux density vector of an electromagnetic wave representing the electromagnetic power transmitted per unit area perpendicular to propagation: $\mathbf{\wp} = \mathbf{E} \times \mathbf{H}$.

Logarithmic decrement ($\delta$)

A dimensionless parameter characterizing the damping rate of an oscillation, defined as the natural logarithm of the ratio of two consecutive amplitudes separated by one full period: $\delta = \ln\left(\frac{A(t)}{A(t+T)}\right) = \beta T$.

Parametric resonance

An oscillatory phenomenon in which the vibration amplitude of a system increases sharply due to the periodic variation of one of the system's own physical parameters (such as pendulum length, capacitance, or inductance) at an appropriate frequency.

Standing wave

A wave pattern produced by the interference of two identical plane waves traveling with equal amplitude and frequency in opposite directions, characterized by stationary positions of zero amplitude (nodes) and maximum amplitude (antinodes).

Doppler effect

The observed frequency shift of a wave received by a detector relative to the source frequency when the source, the receiver, or both are in motion relative to the transmission medium, governed by $\nu' = \frac{v + u'}{v - u} \nu$.