Maharashtra HSC Physics flashcards

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

Moment of inertia

The rotational analogue of mass: I = Σmᵢrᵢ². It measures resistance to angular acceleration and depends on the axis chosen.

Radius of gyration

The distance K from the axis at which the whole mass could be concentrated to give the same moment of inertia: K = √(I/M).

Rolling without slipping condition

The contact point is instantaneously at rest, so v = Rω and a = Rα. Static friction provides the torque but does no work.

Bernoulli's theorem

For steady, non-viscous, incompressible flow, P + ½ρv² + ρgh is constant along a streamline, linking pressure, speed and height.

Terminal velocity

The constant speed reached when viscous drag plus buoyancy balances weight: v_t = 2r²(ρ − σ)g/(9η), proportional to the square of the radius.

Surface tension

Force per unit length along a liquid surface, T = F/L, arising from unbalanced molecular attraction; it makes drops spherical and causes capillarity.

Root-mean-square speed

v_rms = √(3RT/M) = √(3k_BT/m), the speed whose square equals the mean of the squared molecular speeds in an ideal gas.

Degrees of freedom

The number of independent ways a molecule can store energy. Monatomic gases have 3, diatomic 5 at ordinary temperature, polyatomic 6.

Stefan-Boltzmann law

A black body radiates power P = σAT⁴, with σ = 5.67 × 10⁻⁸ W m⁻² K⁻⁴; the fourth-power dependence makes temperature dominant.

First law of thermodynamics

Energy conservation for thermal processes: ΔQ = ΔU + ΔW, where heat absorbed raises internal energy and does work by expansion.

Carnot efficiency

The maximum efficiency of a heat engine between reservoirs at absolute temperatures T₁ and T₂ is η = 1 − T₂/T₁.

Adiabatic process

A process with no heat exchange (Q = 0). Then ΔU = −W and PV^γ = constant, with γ = C_P/C_V.

Simple harmonic motion

Oscillation in which acceleration is proportional to displacement and oppositely directed: a = −ω²x, giving sinusoidal motion about the mean position.

Period of a simple pendulum

T = 2π√(L/g) for small angular amplitude; the period is independent of the bob's mass and of the amplitude.

Resonance

The large-amplitude response that occurs when the driving frequency of a forced oscillation equals the system's natural frequency, especially with light damping.

Stationary wave

A pattern formed by two identical waves travelling in opposite directions, with fixed nodes and antinodes and no net energy transport.

Beat frequency

The number of loudness maxima heard per second when two sounds of slightly different frequency superpose; it equals the difference of the frequencies.

Fundamental frequency of a stretched string

f = (1/2L)√(T/μ), where L is length, T tension and μ mass per unit length; all integer harmonics are present.

Fringe width in Young's experiment

The spacing between successive bright or dark fringes is W = λD/d, where D is slit-to-screen distance and d slit separation.

Brewster's law

At the polarising angle θ_p, tan θ_p = μ. Light reflected at this angle is completely plane polarised, and reflected and refracted rays are perpendicular.

Gauss's law

The total electric flux through a closed surface equals the enclosed charge divided by ε₀, regardless of the surface's shape.

Capacitance

The charge stored per unit potential difference, C = Q/V; for a parallel-plate capacitor in vacuum C = ε₀A/d.

Drift velocity

The small average velocity of free electrons along a conductor under an applied field, related to current by I = nAev_d.

Kirchhoff's junction rule

The algebraic sum of currents at any junction is zero, expressing conservation of charge in a steady-current circuit.

Biot-Savart law

The magnetic field due to a current element is dB = (μ₀/4π)(I dl sinθ)/r², directed perpendicular to the element and the position vector.

Force between parallel currents

Two long parallel wires separated by d exert force per unit length μ₀I₁I₂/2πd; same-direction currents attract, opposite currents repel.

Lenz's law

The induced current flows in a direction that opposes the change in magnetic flux producing it, a consequence of energy conservation.

Resonance in series LCR

At ω₀ = 1/√(LC) the reactances cancel, impedance equals R and is minimum, so current is maximum and the circuit is resistive.

Photoelectric work function

The minimum energy needed to eject an electron from a metal surface, φ₀ = hν₀, where ν₀ is the threshold frequency.

de Broglie wavelength

A particle of momentum p has associated wavelength λ = h/p, so faster or heavier particles have shorter wavelengths.

Bohr quantisation condition

The electron's angular momentum in an allowed orbit is mvr = nh/2π, which produces discrete stable orbits and line spectra.

Rydberg formula

The reciprocal wavelength of a hydrogen spectral line is 1/λ = R(1/n₁² − 1/n₂²), with R about 1.097 × 10⁷ m⁻¹.

Half-life

The time in which half the radioactive nuclei in a sample decay; T₁/₂ = 0.693/λ, where λ is the decay constant.

Binding energy per nucleon

The total nuclear binding energy divided by mass number. It peaks near iron-56, so fusion of light nuclei and fission of heavy ones release energy.

Zener diode

A heavily doped diode operated in reverse breakdown, where voltage stays nearly constant, so it serves as a voltage regulator.

Transistor current gain beta

In common-emitter configuration, β = I_C/I_B, the ratio of collector current to base current; it is related to α by β = α/(1 − α).