Érettségi Physics flashcards

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

Average velocity

Total displacement divided by total elapsed time; a vector quantity, distinct from average speed, which uses total path length and is always non-negative.

Newton's first law

A body remains at rest or moves uniformly in a straight line unless a net external force acts on it; this defines inertial reference frames.

Elastic collision

A collision in which both total momentum and total kinetic energy are conserved; in one dimension equal masses exchange velocities when one is initially at rest.

Centre of mass

The point where the whole mass of a body may be considered concentrated for translational motion; for a uniform gravitational field it coincides with the centre of gravity.

Static friction limit

The maximum static friction force equals μs times the normal force; below this limit the friction force adjusts to balance the applied force exactly.

Absolute zero

The temperature 0 K = −273.15 °C at which molecular translational motion reaches its minimum; it cannot be reached in a finite number of steps.

Specific heat capacity

The heat needed to raise the temperature of one kilogram of a substance by one kelvin, measured in J/(kg·K); water's value is about 4200 J/(kg·K).

Latent heat of fusion

The heat per kilogram required to melt a solid at its melting point without changing temperature; for ice it is about 334 kJ/kg.

Isothermal process

A process at constant temperature; for an ideal gas the internal energy stays constant, so all heat absorbed is converted into work done by the gas.

Second law of thermodynamics

No process can convert heat completely into work in a cyclic engine; entropy of an isolated system does not decrease, fixing the arrow of spontaneous change.

Electric field strength

The force per unit positive charge at a point, E = F/q, measured in V/m or N/C; field lines point away from positive and toward negative charges.

Kirchhoff's loop rule

Around any closed circuit loop the algebraic sum of potential differences is zero; it expresses conservation of energy for charge carriers.

Lorentz force

The force on a charge q moving with velocity v in fields E and B: F = qE + qv×B; the magnetic part is perpendicular to both v and B.

Faraday's law of induction

The induced emf in a loop equals the negative rate of change of magnetic flux through it, multiplied by the number of turns.

Lenz's law

The direction of an induced current is such that its magnetic effect opposes the change in flux that produced it, a consequence of energy conservation.

Total internal reflection

When light travels from a denser to a rarer medium beyond the critical angle, no light refracts out and the interface reflects it entirely.

Refractive index

The ratio n = c/v of light speed in vacuum to that in the medium; it determines bending at an interface through Snell's law.

Diffraction

The spreading of waves around obstacles and through apertures, noticeable when the obstacle or slit size is comparable to the wavelength.

Doppler effect

The change in observed frequency when source and observer move relative to each other; approach raises the frequency, recession lowers it.

Converging lens

A lens thicker at the centre with positive focal length; it forms a real inverted image of an object beyond the focal point and a virtual magnified one inside it.

Photoelectric threshold

The minimum frequency of light that can eject electrons from a metal surface, equal to the work function divided by Planck's constant.

Half-life

The time in which half of the radioactive nuclei in a sample decay; after n half-lives the remaining fraction is (1/2)^n.

Alpha particle

A helium-4 nucleus emitted in alpha decay, carrying charge +2e; its emission lowers mass number by four and atomic number by two.

de Broglie wavelength

The wavelength associated with a particle of momentum p, given by λ = h/p; it explains electron diffraction and quantised atomic energy levels.

Binding energy per nucleon

The energy needed to remove one nucleon from a nucleus, peaking near iron-56; higher values mean greater nuclear stability.

Kepler's third law

The square of an orbital period is proportional to the cube of the semi-major axis; for the solar system T²/a³ is the same for all planets.

Escape velocity

The minimum speed needed to leave a body's gravitational field without further propulsion, equal to √(2GM/R); Earth's value is about 11.2 km/s.

Geostationary orbit

A circular equatorial orbit with a period of one sidereal day, so the satellite stays above the same point; its radius is about 42,000 km.

Hubble's law

Recession speed of distant galaxies is proportional to their distance, v = H₀d, with H₀ near 70 km/s/Mpc; evidence for cosmic expansion.

Dimensional analysis

Checking an equation by comparing base-unit exponents on both sides; it detects errors in form but cannot determine dimensionless constants.

Ideal transformer

A device with voltage ratio equal to turns ratio, U₁/U₂ = N₁/N₂; an ideal one conserves power, so current scales inversely with voltage.

Measurement uncertainty

The interval within which the true value probably lies; for a single analogue reading it is typically half the smallest scale division.

Kilowatt-hour

A practical energy unit equal to 3.6×10⁶ J, the energy a 1 kW device uses in one hour; it is the unit on household electricity bills.