Cambridge OCR A Level Physics A (H556) Specification Flashcards

Flashcards covering core vocabulary, physical laws, and definitions from the Cambridge OCR A Level Physics A (H556) specification.

Système Internationale (S.I.) base units

The seven fundamental units: mass ($kg$), length ($m$), time ($s$), current ($A$), temperature ($K$), and amount of substance ($mol$).

Homogeneity of equations

The requirement that both sides of a physical equation must have the same S.I. base units.

Systematic Error

A constant error in all measurements, including zero errors, which affects the accuracy of the result.

Scalar quantity

A physical quantity that has magnitude but no direction.

Vector quantity

A physical quantity that possesses both magnitude and direction.

Terminal velocity

The constant maximum velocity of an object falling through a fluid when the drag force equals the weight.

Newton

The S.I. unit of force; one newton is the force required to accelerate a mass of $1\,kg$ at a rate of $1\,m/s^2$.

Archimedes’ principle

The principle stating that the upthrust on an object in a fluid is equal to the weight of the fluid displaced.

Moment of force

The product of the force and the perpendicular distance from the pivot to the line of action of the force ($Moment = Fx$).

Couple

A pair of equal and parallel but opposite forces that tend to produce rotation only.

Principle of conservation of energy

Energy cannot be created or destroyed, only transferred into different forms.

Hooke’s law

The extension of a spring is directly proportional to the force applied to it, provided the elastic limit is not exceeded ($F = kx$).

Young modulus

The ratio of tensile stress to tensile strain for a material ($E = \frac{\sigma}{\epsilon}$).

Impulse

The product of the net force acting on an object and the time for which it acts ($Impulse = F\Delta t$), equal to the change in momentum.

Kirchhoff’s first law

The sum of the currents entering any junction is equal to the sum of the currents leaving that junction, representing the conservation of charge.

Kirchhoff’s second law

In any closed loop, the sum of the e.m.f.s is equal to the sum of the potential differences, representing the conservation of energy.

Mean drift velocity

The average velocity attained by charge carriers, such as electrons, in a material due to an electric field ($I = Anev$).

Electromotive force (e.m.f.)

The energy transferred per unit charge from some other form of energy into electrical energy.

Internal resistance

The resistance to electric current within the source of e.m.f. itself, resulting in 'lost volts'.

Progressive wave

A wave that transfers energy from one point to another without transferring matter.

Coherence

Two sources of waves are coherent if they maintain a constant phase difference.

Stationary (standing) wave

The superposition of two progressive waves of the same frequency travelling in opposite directions, characterized by nodes and antinodes.

Photon

A quantum of electromagnetic radiation with energy proportional to its frequency ($E = hf$).

Work function ($\phi$)

The minimum energy required to remove an electron from the surface of a metal.

De Broglie equation

The relationship used to determine the wavelength of a particle based on its momentum ($\lambda = \frac{h}{p}$).

Thermal equilibrium

The state in which there is no net flow of thermal energy between two objects because they are at the same temperature.

Specific heat capacity

The energy required per unit mass to increase the temperature of a material by one degree ($E = mc\Delta \theta$).

Simple harmonic motion (SHM)

Oscillatory motion where the acceleration is directly proportional to the displacement from the equilibrium position and is always directed towards that position ($a = -\omega^2 x$).

Kepler’s third law

The square of a planet's orbital period ($T^2$) is directly proportional to the cube of its average distance ($r^3$) from the Sun.

Wien’s displacement law

The relationship stating that the peak wavelength of radiation from a black body is inversely proportional to its absolute temperature ($\lambda_{max} \propto \frac{1}{T}$).

Time constant ($\tau$)

For a capacitor-resistor circuit, it is the product of the capacitance and the resistance ($\tau = CR$).

Coulomb’s law

The electrical force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them ($F = \frac{Qq}{4\pi\epsilon_0 r^2}$).

Faraday’s law

The magnitude of the induced e.m.f. is directly proportional to the rate of change of magnetic flux linkage.

Lenz’s law

The direction of an induced e.m.f. is such that it would oppose the change of magnetic flux that caused it.

Hadrons

Particles and antiparticles that are subject to both the strong nuclear force and the weak nuclear force.

Leptons

Fundamental particles, such as electrons and neutrinos, that are subject to the weak nuclear force but not the strong nuclear force.

Acoustic impedance

The product of the density of a medium and the speed of ultrasound in that medium ($Z = \rho c$).