Physics terms starting with D

Electromagnetism & Electronics

Displacement Current

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) A (Amperes)

Mathematical & Computational Physics

Divergence

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) [Vector Field Unit] / m

Mathematical & Computational Physics

Divergence Theorem

A fundamental theorem of vector calculus stating that the outward flux of a vector field through a closed surface ∂V equals the volume…

∯_(∂V) F · dA = ∭_V (∇ · F) dV Vector Integral Theorem

Plasma Physics

Divertor

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 MW/m² (Heat Flux Capacity)

Biophysics & Medical Physics

DNA Biophysics

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 nm (Persistence Length) & pN (Stretching Force)

Condensed Matter & Materials Physics

Doping

The intentional insertion of trace impurity atoms into an intrinsic semiconductor lattice to drastically modulate its electrical…

N_D (Donors) or N_A (Acceptors) ~ 10¹⁴ to 10¹⁹ cm⁻³ Atoms/cm³ (Dopant Concentration)

Waves, Oscillations & Acoustics

Doppler Effect

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) Hz

Classical Mechanics

Drag Force

The fluid resistance force opposing the motion of an object moving through a liquid or gas.

Fd = ½ ρ v² Cd A N

Astrophysics, Cosmology & Relativity

Drake Equation

A probabilistic equation formulated by Frank Drake in 1961 to estimate the number N of active, communicative extraterrestrial civilizations…

N = R* · f_p · n_e · f_l · f_i · f_c · L Number of Civilizations N

Condensed Matter & Materials Physics

Ductility

A material's mechanical capability to undergo significant plastic strain deformation under tensile stress before fracturing.

% Elongation = ((L_break - L₀) / L₀) × 100% % (Percent Elongation or Area Reduction)

Plasma Physics

Dusty Plasma

A complex plasma containing solid nanometer-to-micrometer scale dust grains that collect high negative charges from surrounding plasma…

Q_dust ~ - 10³ e to - 10⁵ e (Charged Micron Dust Grains) μm (Dust Size) & Charged State