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Terms starting with P

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Condensed Matter & Materials Physics

P-type Semiconductor

An extrinsic semiconductor in which trivalent acceptor impurities create an excess concentration of positive holes as majority charge…

p ≈ N_A ≫ n, n p = n_i² cm⁻³ (Hole Concentration)
Geophysics & Environmental Physics

Paleoclimatology

The scientific study of Earth's past climate conditions across geologic history using indirect environmental proxy records.

Climate Proxies: Ice Cores, Tree Rings, Coral δ¹⁸O, Speleothems Geologic Climate History
Geophysics & Environmental Physics

Paleomagnetism

The study of the historical record and orientation of Earth's magnetic field preserved in iron-bearing minerals in rocks, sediments, or…

Remanent Magnetization Vector (Declination & Inclination) Degrees (° Declination / Inclination)
Classical Mechanics

Parallel Axis Theorem

A theorem stating that the moment of inertia about any axis parallel to a centroidal axis equals the centroidal moment of inertia plus mass…

I = I_cm + M d² kg·m²
Electromagnetism & Electronics

Parallel Circuit

An electrical circuit topology in which components are connected across common voltage nodes, offering multiple parallel paths for current.

1 / R_total = (1/R₁) + (1/R₂) + (1/R₃), V_total = V₁ = V₂ = V₃ Ω (Ohms)
Mathematical & Computational Physics

Parallel Computing

A computational architecture where large physical calculations are divided into smaller sub-tasks executed simultaneously across multiple…

Amdahl's Law Speedup S(P) = 1 / ((1 - p) + p / P) Speedup Factor S(P)
Electromagnetism & Electronics

Paramagnetism

A weak form of magnetism in which materials with unpaired electrons are weakly attracted into an external magnetic field.

χ_m = C / T (Curie's Law) Dimensionless (χ_m > 0)
Optics

Paraxial Approximation

A small-angle approximation in geometric optics assuming light rays make small angles $θ$ with the optical axis.

sin θ ≈ θ, tan θ ≈ θ, cos θ ≈ 1 rad (radians)
Nuclear & Particle Physics

Parity Violation

The discovery that the weak nuclear force distinguishes between left-handed and right-handed spatial orientations, violating spatial mirror…

P |Ψ(x, y, z)⟩ = - |Ψ(-x, -y, -z)⟩ (Violated in weak decays) Symmetry Violation
Astrophysics, Cosmology & Relativity

Parsec

An astronomical unit of distance equal to the distance at which a star exhibits a trigonometric parallax angle of exactly one arcsecond…

1 pc = 1 AU / tan(1″) ≈ 3.2616 ly ≈ 3.0857 × 10¹⁶ m Parsecs (pc, kpc, Mpc)
Mathematical & Computational Physics

Partial Differential Equations

Differential equations containing unknown multivariable functions and their partial derivatives with respect to multiple independent…

Elliptic (Laplace), Parabolic (Heat), Hyperbolic (Wave) Multivariable Differential Equations
Quantum & Atomic Physics

Particle in a Box

A elementary quantum model describing a particle trapped inside a 1D rigid box with impenetrable potential barriers (infinite potential…

E_n = (n² π² ℏ²) / (2 m L²), ψ_n(x) = √(2/L) sin(n π x / L) eV or Joules
Thermodynamics & Statistical Physics

Partition Function

The central mathematical function in statistical mechanics that encodes statistical properties of a system in thermodynamic equilibrium.

Z = ∑ exp(-E_i / (kB T)) = ∑ g_i exp(-E_i / (kB T)) Dimensionless
Classical Mechanics

Pascal's Principle

The principle stating that pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and container…

ΔP = F1 / A1 = F2 / A2 Pa
Quantum & Atomic Physics

Paschen Series

The spectral series of hydrogen atom emission lines produced by electron transitions dropping from upper energy states to the n=3 level.

1 / λ = R_H (1 / 3² - 1 / n_i²), n_i = 4, 5, 6... Infrared Wavelengths (nm)
Biophysics & Medical Physics

Patch Clamp Technique

An electrophysiological laboratory technique used to record ion currents flowing through single individual ion channel proteins in cell…

I_single_channel ~ 1–10 pA (Gigaohm Seal Measurement) pA (Picoamperes) & GΩ (Gigaohm Resistance)
Quantum & Atomic Physics

Pauli Exclusion Principle

A fundamental quantum law stating that two identical fermions cannot occupy the exact same quantum state simultaneously.

No two identical fermions can occupy the same quantum state: ψ(1,2) = -ψ(2,1) Dimensionless Quantum Law
Condensed Matter & Materials Physics

Peltier Effect

The absorption or emission of heat at the junction of two dissimilar electrical conductors when an electric current flows across it.

Q_rate = Π_AB I = (S_A - S_B) T I W (Cooling / Heating Rate)
Foundations of Physics

Percentage Uncertainty

The absolute uncertainty of a measurement divided by the measured value, expressed as a percentage.

Percentage Uncertainty = (Δx / x) × 100% %
Classical Mechanics

Period

The time duration required to complete one full cycle of a recurring motion or oscillation.

T = 1 / f = 2π / ω = 2π √(m/k) s
Classical Mechanics

Perpendicular Axis Theorem

A theorem stating that for a thin planar lamina, the moment of inertia about an axis perpendicular to the plane equals the sum of moments…

Iz = Ix + Iy kg·m²
Mathematical & Computational Physics

Perturbation Theory

A set of mathematical approximation methods for finding an approximate solution to a complex problem by starting from the exact solution of…

H = H₀ + λ H', E_n = E_n^(0) + λ E_n^(1) + λ² E_n^(2) + ... Approximation Power Series
Waves, Oscillations & Acoustics

Phase

The fractional position of a point within a wave cycle, expressed as an angle relative to a reference origin.

Φ(x,t) = k x - ω t + φ0 rad (radians)
Waves, Oscillations & Acoustics

Phase Difference

The angular difference between corresponding points on two waves or between different points on a single wave.

Δφ = (2π / λ) Δx = (2π / T) Δt rad (radians)