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Electromagnetism & Electronics

Coulomb's Law

An inverse-square law stating that the electrostatic force between two stationary point charges is directly proportional to the product of…

F = k_e |q₁ q₂| / r² = (1 / (4π ε₀)) |q₁ q₂| / r² N (Newtons) Classical Mechanics

Couple

A system of two equal, parallel forces acting in opposite directions whose lines of action do not coincide, producing pure torque without…

τ = F d N·m Nuclear & Particle Physics

Coupling Constant

A dimensionless number quantifying the relative interaction strength between particles or fields in a fundamental force interaction.

α_EM = e² / (4π ε₀ ℏ c) ≈ 1 / 137, α_s(Q²) Dimensionless Parameter Condensed Matter & Materials Physics

Creep

The slow, time-dependent permanent plastic deformation of a solid material subjected to long-term mechanical stresses below its yield…

ε_creep = A σ^n e^(-Q / (R T)) (Power law creep) s⁻¹ (Creep Strain Rate) Optics

Critical Angle

The specific angle of incidence in an optically denser medium for which the angle of refraction in the rarer medium is exactly 90 degrees.

θ_c = arcsin(n2 / n1) Degrees (°) Nuclear & Particle Physics

Critical Mass

The minimum mass of fissile material required to sustain a continuous self-sustaining nuclear chain reaction.

Neutron Leakage Rate = Neutron Production Rate (k = 1) kg (Kilograms) Thermodynamics & Statistical Physics

Critical Point

The endpoint of a phase equilibrium curve in a P-T phase diagram where coexisting liquid and vapor phases become indistinguishable.

(∂P/∂V)_T = 0, (∂²P/∂V²)_T = 0 Pa, K Geophysics & Environmental Physics

Cryosphere

The collective portion of Earth's surface where water exists in solid frozen form.

Components: Sea Ice, Glaciers, Ice Sheets, Permafrost, Snow Cover km² (Spatial Extent) or Gt (Mass) Condensed Matter & Materials Physics

Crystal Structure

The ordered, periodic three-dimensional arrangement of atoms, ions, or molecules in a crystalline solid.

Crystal Structure = Lattice + Basis Å or nm (Lattice Parameters a, b, c) Condensed Matter & Materials Physics

Curie-Weiss Law

A thermodynamic law describing the magnetic susceptibility of a ferromagnetic or antiferromagnetic material in its paramagnetic phase above…

χ_m = C / (T - T_C) (for T > T_C) Dimensionless (Magnetic Susceptibility) Mathematical & Computational Physics

Curl

A vector differential operator measuring the local circulation or rotation density of a 3D vector field around a point.

curl F = ∇ × F = det|[î, ĵ, k̂], [∂/∂x, ∂/∂y, ∂/∂z], [F_x, F_y, F_z]| [Vector Field Unit] / m Mathematical & Computational Physics

Curve Fitting

The mathematical construction of a function that best matches a set of experimental data points according to statistical criteria.

Minimizing χ² = ∑ ((y_i - f(x_i, θ)) / σ_i)² Goodness of Fit χ² Electromagnetism & Electronics

Cyclotron

A particle accelerator in which charged particles orbit spirally in a constant magnetic field while high-frequency AC electric fields…

f_c = (q B) / (2π m), KE_max = (q² B² R²) / (2 m) Hz (Frequency), J or MeV (Kinetic Energy) Plasma Physics

Cyclotron & Synchrotron Emission

Electromagnetic radiation emitted by charged particles undergoing gyromotion acceleration around magnetic field lines in a plasma.

P_rad = (2 e⁴ B² v_⊥²) / (3 m_e² c³) (Non-relativistic Cyclotron) W (Radiated Power) Nuclear & Particle Physics

Cyclotron (Particle Physics)

A circular particle accelerator using a perpendicular magnetic field to bend charged particles into spiral paths while high-frequency AC…

f_c = (q B) / (2π m), KE_max = (q² B² R²) / (2 m) MeV (Beam Energy) Foundations of Physics

Cylindrical Coordinates

A 3D coordinate system combining 2D polar coordinates (r, θ) in the transverse plane with a linear vertical height axis z.

x = r cos θ, y = r sin θ, z = z m, rad, m Biophysics & Medical Physics

Cytoskeleton Mechanics

The study of the mechanical properties, viscoelasticity, and force generation of the intracellular filament network (actin, microtubules…

Flexural Rigidity EI = E_young × I_area_moment pN·μm² (Bending Stiffness) Waves, Oscillations & Acoustics

Damped Oscillations

Oscillatory motion whose mechanical energy and amplitude decrease exponentially over time due to dissipative forces like friction or…

x(t) = A exp(-b t / 2m) cos(ω_d t + φ) m Geophysics & Environmental Physics

Darcy's Law

A foundational hydrogeological equation describing the flow rate of fluid through a porous medium under a hydraulic gradient.

Q = -K A (dh / dl), q = Q / A = -K ∇h m/s (Darcy Flux q) Astrophysics, Cosmology & Relativity

Dark Energy

An unknown form of energy with negative pressure that permeates all space and drives the accelerated expansion of the universe.

Ω_Λ ≈ 0.68, w = P / ρ ≈ -1 Cosmological Constant Λ (J/m³) Astrophysics, Cosmology & Relativity

Dark Matter

A non-baryonic form of matter that does not absorb, reflect, or emit electromagnetic radiation, detectable solely through its gravitational…

Ω_dm ≈ 0.27 (27% of total cosmic mass-energy) M_☉ or kg (Cosmological Density) Astrophysics, Cosmology & Relativity

Dark Matter Halo

An extended, nearly spherical region of dark matter enveloping a galaxy or galaxy cluster that extends far beyond the visible stellar disk.

NFW Density Profile: ρ(r) = ρ₀ / ((r/r_s) (1 + r/r_s)²) kpc (Halo Radius) & M_☉ (Halo Mass) Quantum & Atomic Physics

Davisson-Germer Experiment

A 1927 physics experiment that experimentally confirmed De Broglie's matter wave hypothesis by demonstrating electron diffraction from a…

n λ = 2 d sin θ = h / p nm (Wavelength) Quantum & Atomic Physics

De Broglie Wavelength

The wavelength associated with a massive particle, expressing its intrinsic wave-like character.

λ = h / p = h / (m v) m or nm (Wavelength)