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842 terms · page 16 of 36


A–Z
All A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Classical Mechanics

Inelastic Collision

A collision in which total linear momentum is conserved, but total kinetic energy is not conserved.

∑ p_i = ∑ p_f, KE_final < KE_initial kg·m/s, J
Classical Mechanics

Inertia

The natural resistance of any physical object to any change in its velocity or state of motion.

Quantified by Mass (m) kg
Plasma Physics

Inertial Confinement Fusion

A fusion energy approach that uses intense laser or ion beam pulses to rapidly compress and heat a millimeter-scale fuel capsule to fusion…

ρ R ≥ 1 g/cm² (Compressed Areal Density) g/cm² (Areal Density) & Mbar (Implosion Pressure)
Foundations of Physics

Inertial Mass

A measure of an object's intrinsic resistance to changes in its velocity when subjected to a net force.

m = F / a kg
Geophysics & Environmental Physics

Insolation

The solar electromagnetic radiation power reaching a specified surface area per unit time.

S = S₀ (R₀ / R)² cos Z W/m² or kWh/m²/day
Thermodynamics & Statistical Physics

Intensive vs Extensive Properties

Classification of thermodynamic properties based on whether they depend on system size or amount of matter.

Extensive: U, V, S, m, H; Intensive: T, P, ρ, μ Various
Plasma Physics

Interchange & Flute Instabilities

A magnetohydrodynamic (MHD) instability where high-pressure plasma and low-density magnetic fields interchange spatial positions in regions…

Bad Curvature Condition: (∇P) · (∇B) > 0 MHD Flute Mode Instability
Thermodynamics & Statistical Physics

Internal Energy

The total microscopic energy contained within a thermodynamic system, comprising kinetic energies of particle…

U = (f/2) n R T (for ideal gas) J
Condensed Matter & Materials Physics

Intrinsic Semiconductor

An ultra-pure semiconductor crystal containing no significant dopant impurity species, where carrier concentration is determined purely by…

n = p = n_i = √(N_c N_v) e^(-E_g / (2 k_B T)) cm⁻³ (Carrier Density)
Biophysics & Medical Physics

Ion Channels

Pore-forming transmembrane proteins that allow selective passive passage of specific ions down their electrochemical gradient.

I_channel = g_channel (V_m - E_ion) pS (Picosiemens Conductance) & pA (Current)
Plasma Physics

Ionization Energy

The minimum energy required to detach an electron from a neutral atom or ion, initiating gas-to-plasma phase transformation.

E_ion = h ν - K_e (Saha Ionization Equation) eV (Electron-Volts)
Geophysics & Environmental Physics

Ionosphere

An ionized layer of Earth's upper atmosphere (~60 km to 1,000 km) where extreme solar UV and X-ray radiation ionize atmospheric gas atoms…

Plasma Frequency f_p = (1 / 2π) √(n_e e² / (ε₀ m_e)) Electrons/m³ (Electron Density n_e)
Geophysics & Environmental Physics

Ionospheric Scintillation

Rapid fluctuations in amplitude and phase of satellite radio signals caused by small-scale electron density irregularities in the…

Scintillation Index S₄ = √(⟨I²⟩ - ⟨I⟩²) / ⟨I⟩ Dimensionless S₄ Index
Thermodynamics & Statistical Physics

Isobaric Process

A thermodynamic change in state occurring under constant pressure conditions.

ΔP = 0, W = P ΔV, Q = ΔH = n Cp ΔT J
Nuclear & Particle Physics

Isobars

Nuclides of different chemical elements that share the exact same mass number A (total number of nucleons) while having different atomic…

A = Z + N = Constant Dimensionless Species
Thermodynamics & Statistical Physics

Isochoric Process

A thermodynamic process occurring at constant volume, during which no mechanical boundary work is performed.

ΔV = 0 ⇒ W = 0, Q = ΔU = n Cv ΔT J
Geophysics & Environmental Physics

Isostasy

The state of gravitational equilibrium between Earth's lithospheric crust blocks floating at depths determined by their thickness and…

Airy Model: h_root = h_mountain (ρ_crust / (ρ_mantle - ρ_crust)) Meters (Crustal Root Depth)
Thermodynamics & Statistical Physics

Isothermal Process

A thermodynamic change in state occurring at a constant temperature throughout the system.

ΔT = 0 ⇒ ΔU = 0, Q = W = n R T ln(V2/V1) J
Nuclear & Particle Physics

Isotones

Nuclides of different chemical elements that share the exact same number of neutrons N = A - Z while possessing different proton numbers Z.

N = A - Z = Constant Dimensionless Species
Nuclear & Particle Physics

Isotopes

Variants of a particular chemical element that possess identical atomic numbers Z (same number of protons) but different mass numbers A…

Nuclide Symbol: ᴬ_Z X (Same Z, Different A) Dimensionless Species
Mathematical & Computational Physics

Jacobian Matrix

A matrix of all first-order partial derivatives of a vector-valued multivariable function, representing local linear coordinate…

J_ij = ∂f_i / ∂x_j, dV' = |det J| dV Coordinate Transformation Factor
Condensed Matter & Materials Physics

Josephson Effect

The quantum tunneling of Cooper pairs across a thin insulating barrier separating two superconductors (a Josephson junction).

I = I_c sin(Δφ), V = (ℏ / 2e) (dΔφ / dt) mA (Current), μV (Voltage)
Electromagnetism & Electronics

Joule Heating

The process in which the flow of electric current through a conductor generates thermal energy due to electrical resistance.

H = I² R t = P t J (Joules)
Thermodynamics & Statistical Physics

Joule-Thomson Effect

The temperature change experienced by a real gas when throttled through an insulated porous plug or valve at constant enthalpy.

μ_JT = (∂T / ∂P)_H K/Pa