AP Physics 2 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

First Law of Thermodynamics

The change in internal energy of a system equals heat added to the system minus work done by the system: ΔU = Q − W.

Isothermal Process

A process at constant temperature. For an ideal gas ΔU = 0, so heat absorbed equals work done: Q = W = nRT ln(V_f/V_i).

Adiabatic Process

A process with no heat exchange (Q = 0). Then ΔU = −W, and for an ideal gas the product PV^γ stays constant.

Carnot Efficiency

The maximum possible efficiency of a heat engine operating between hot and cold reservoirs: e = 1 − T_C/T_H, with temperatures in kelvin.

Coulomb's Law

The electrostatic force between two point charges is F = kq₁q₂/r², attractive for opposite signs and repulsive for like signs.

Electric Field of Point Charge

The field at distance r from charge q is E = kq/r², pointing away from positive charge and toward negative charge.

Electric Potential of Point Charge

The potential at distance r from charge q is V = kq/r. Potential is a scalar, so contributions from multiple charges add algebraically.

Gauss's Law

The electric flux through a closed surface equals the enclosed charge divided by ε₀, enabling field calculation for symmetric distributions.

Capacitor Energy Storage

A capacitor stores energy U = (1/2)CΔV² = Q²/(2C). For a parallel-plate capacitor, C = ε₀A/d.

Resistors in Parallel

Reciprocals add: 1/R_eq = 1/R₁ + 1/R₂ + … The equivalent resistance is always less than the smallest individual resistance.

Kirchhoff's Loop Rule

Around any closed circuit loop, the algebraic sum of potential differences is zero, expressing conservation of energy in the circuit.

RC Time Constant

For a resistor-capacitor circuit, τ = RC. In one time constant a charging capacitor reaches about 63% of its final charge.

Electrical Power Dissipation

Power converted to thermal energy in a resistor is P = IV = I²R = V²/R, where V is the voltage across that resistor.

Magnetic Force on Moving Charge

A charge moving in a magnetic field feels F = qvB sinθ, directed perpendicular to both velocity and field by the right-hand rule.

Charged Particle Circular Motion

A charge moving perpendicular to a uniform magnetic field travels in a circle of radius r = mv/(qB), with period independent of speed.

Faraday's Law of Induction

The induced emf in a loop equals the negative rate of change of magnetic flux through it: emf = −N dΦ_B/dt.

Lenz's Law

The direction of an induced current is such that its magnetic field opposes the change in flux that produced the current.

Motional EMF

A conducting rod of length L moving at speed v perpendicular to a magnetic field B develops an emf equal to BLv.

Snell's Law

At an interface, n₁ sinθ₁ = n₂ sinθ₂, where angles are measured from the normal and n is the index of refraction.

Total Internal Reflection

Occurs only when light travels from higher to lower index and the incident angle exceeds the critical angle sinθ_c = n₂/n₁.

Thin Lens Equation

1/f = 1/d_o + 1/d_i relates focal length, object distance, and image distance. Magnification is m = −d_i/d_o.

Real Versus Virtual Image

A real image is formed by actually converging rays and can be projected on a screen; a virtual image cannot.

Double-Slit Interference

Constructive interference occurs when d sinθ = mλ; destructive when d sinθ = (m + 1/2)λ, for slit separation d.

Thin-Film Phase Shift

Reflection from a medium of higher index shifts the reflected wave by half a wavelength, affecting thin-film interference conditions.

Standing Waves on a String

A string fixed at both ends supports wavelengths λ_n = 2L/n, with n equal to the number of antinodes in the mode.

Doppler Effect

The observed frequency rises when source and observer approach and falls when they recede, depending on relative motion through the medium.

Diffraction Grating Maxima

Bright principal maxima occur where d sinθ = mλ; increasing the number of slits makes each maximum narrower and sharper.

Photoelectric Effect

Light ejects electrons with maximum kinetic energy K = hf − φ. Below the threshold frequency, no electrons are emitted at any intensity.

Photon Energy

A photon carries energy E = hf = hc/λ and momentum p = h/λ, where h is Planck's constant.

de Broglie Wavelength

Any particle with momentum p has an associated wavelength λ = h/p, observable for electrons and other low-mass particles.

Radioactive Half-Life

The time for half of a sample's radioactive nuclei to decay; related to the decay constant by t₁/₂ = ln2/λ.

Bohr Model Energy Levels

Hydrogen levels follow E_n = −13.6 eV/n². Transitions emit or absorb photons whose energy equals the level difference.