Physics terms starting with D

Displacement Current Electromagnetism & Electronics A (Amperes) A fictitious effective current term introduced by Maxwell to account for magnetic field generation by time-varying electric fields. I_d = ε₀ (dΦ_E / dt)

Divergence Mathematical & Computational Physics [Vector Field Unit] / m A scalar differential operator measuring the net outward flux density of a vector field from an infinitesimal volume around a given point. div F = ∇ · F = (∂F_x/∂x) + (∂F_y/∂y) + (∂F_z/∂z)

Divergence Theorem Mathematical & Computational Physics Vector Integral Theorem A fundamental theorem of vector calculus stating that the outward flux of a vector field through a closed surface ∂V equals the volume integral of its divergence over the enclosed region V. ∯_(∂V) F · dA = ∭_V (∇ · F) dV

Divertor Plasma Physics MW/m² (Heat Flux Capacity) A component in a fusion tokamak that uses magnetic null points (X-points) to extract helium ash and heat exhaust from the plasma edge. Magnetic X-point Separatrix Boundary Geometry

DNA Biophysics Biophysics & Medical Physics nm (Persistence Length) & pN (Stretching Force) The physical study of mechanical stiffness, elasticity, topology, and base-pairing thermodynamics of double-stranded DNA. Persistence Length A_p ≈ 50 nm, Contour Length L

Doping Condensed Matter & Materials Physics Atoms/cm³ (Dopant Concentration) The intentional insertion of trace impurity atoms into an intrinsic semiconductor lattice to drastically modulate its electrical conductivity and charge carrier density. N_D (Donors) or N_A (Acceptors) ~ 10¹⁴ to 10¹⁹ cm⁻³

Doppler Effect Waves, Oscillations & Acoustics Hz The apparent shift in observed wave frequency caused by relative motion between the wave source and the observer. f_obs = f_src (v ± v_obs) / (v ∓ v_src)

Drag Force Classical Mechanics N The fluid resistance force opposing the motion of an object moving through a liquid or gas. Fd = ½ ρ v² Cd A

Drake Equation Astrophysics, Cosmology & Relativity Number of Civilizations N A probabilistic equation formulated by Frank Drake in 1961 to estimate the number N of active, communicative extraterrestrial civilizations in the Milky Way. N = R* · f_p · n_e · f_l · f_i · f_c · L

Ductility Condensed Matter & Materials Physics % (Percent Elongation or Area Reduction) A material's mechanical capability to undergo significant plastic strain deformation under tensile stress before fracturing. % Elongation = ((L_break - L₀) / L₀) × 100%

Dusty Plasma Plasma Physics μm (Dust Size) & Charged State A complex plasma containing solid nanometer-to-micrometer scale dust grains that collect high negative charges from surrounding plasma electrons. Q_dust ~ - 10³ e to - 10⁵ e (Charged Micron Dust Grains)

Dynamic Equilibrium Classical Mechanics N, N·m The state of a physical system moving at constant linear velocity and constant angular velocity with zero net force and zero net torque. ∑ F = 0 (v = const ≠ 0), ∑ τ = 0 (ω = const)

Terms starting with D