Studied by 3 peopleabsolute uncertainty
a quantity giving the extremes a measured value falls within
absolute zero
the temperature at which all random motion of molecules stops
absorption spectra
the set of wavelengths of photons absorbed by a substance
acceleration of free fall
the acceleration due to the pull of the Earth on a body
accurate
a measurement where the systematic error is small and so close to the "true" value
activity
the rate of decay of a radioactive sample
albedo
the ration of scattered to incident intensity of radiation
alpha particle
the nucleus of helium-4
alternating current (ac)
current in which electrons oscillate instead of moving with the same drift speed in the same direction
Amonton's law or Gay-Lussac's law
the relation between pressure and temperature of a fixed quantity of an ideal gas when the volume is kept constant
amplitude
the largest value of the displacement from equilibrium of an oscillation
angular frequency or angular speed
the ratio of angle turned to time taken
angular momentum
the product of mass, speed and orbit radius of a particle
angular separation
the angle that the distance between two objects subtends at the observer's eye
antinode
a point in a medium with a standing wave where the displacement is momentarily a maximum
anti-particle
a particle with the same mass as its particle but with all other properties opposite, such as electric charge
atomic (or proton) number
the number of protons in a nucleus
atomic mass unit
a unit of mass equal to 1/12 the mass of a neutral atom of carbon-12
average speed
the ratio of distance travelled to total time taken
average velocity
the ratio of displacement to total time taken
Avogadro constant
the number of particles in one mole
baryon
a particle made up of three quarks
baryon number
a conserved quantum number; it is assigned to each quark, and by extension to baryons
beta minus decay
a decay producing an electron and an anti-neutrino
beta plus decay
a decay producing a positron and a neutrino
binding energy
the minimum energy that must be supplied to completely separate the nucleons in a nucleus or the energy released when a nucleus is assembled
black body
a theoretical body that reflects none of the radiation incident on it and so absorbs all of it
blue-shift
a decrease in the observed wavelength
boiling
the change from the liquid to the vapour state at a specific constant temperature
Boyle's law
the relation between pressure and volume of a fixed quantity of an ideal gas when temperature is kept constant
capacitance
the charge that can be stored on a capacitor per unit voltage
centripetal acceleration
the acceleration due to a changing direction of velocity
centripetal force
a force pointing to the centre of a circular path
chain reaction
a self-sustaining reaction
charge carrier
charged particles that are able to move, creating an electric current
Charles' law
the relation between volume and temperature of a fixed quantity of an ideal gas when the pressure is kept constant
coefficient of dynamic friction
the ratio of the force of friction to the normal reaction force on a body while the body is sliding on a surface
coefficient of static friction
the ratio of the maximum force of friction that can develop between two bodies to the normal reaction force on a body while the body is at rest
coherent
sources whose phase difference is constant in time
compression
a point in a medium through which a wave is travelling that has maximum density
condensation
the change from the vapour to the liquid state
conduction
the transfer of heat through electron and molecular collisions
conservation of energy
the principle that energy cannot be destroyed or created but can only be changed from one form into another
conservation of momentum
when the net force on a system is zero, the total momentum of the system is constant
conserved
a quantity that states the same before and after an interaction
constructive interference
the superposition of two identical waves that arrive at a point in phase
control rod
a rod that regulates the the rate of energy release in a nuclear fission reactor by regulating the absorption of neutrons
convection current
motion of a fluid as a result of differences in fluid density
convection
the transfer of heat in fluids through differences in fluid density
Coulomb's law
the electric force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation
crest
a point on a wave of maximum displacement
critical angle
the angle of incidence for which the angle of refraction is a right angle
critical mass
the smallest mass of fissionable material that can sustain fission reactions
decay constant
the probability per unit time for a nucleus to decay
destructive interference
the superposition of two identical waves that arrive at a point 180 degrees out of phase
diffraction
the spreading of a wave past an aperture or an obstacle
diffraction grating
a series of very many and very narrow slits
diode
a device that lets current through it only in one direction
diode bridge rectifier
a circuit that achieved full-wave rectification
dipole
a pair of two equal and opposite electric charges
direct current (dc)
current in which electrons move in the same direction with the same average drift speed
discrete
energy that can take a set of specific values as opposed to a continuous range of values
dispersion
the dependence of refractive index on wavelength
displacement
the change in position; for an oscillation, the distance between the position of a particle and its equilibrium position
Doppler effect
the change in measured frequency when there is relative motion between source and observer
drag force
a force of resistance to motion
eddy currents
small induced currents in a conductor where the flux is changing that dissipate energy
efficiency
the ratio of useful work or power to input work or power
elastic potential energy
the energy stored in a spring when it is compressed or stretched
electric field strength
the electric force per unit charge experienced by a small point positive charge
electric potential
the work done per unit charge by and external agent in bringing a small point positive charge from infinity to a point
electric potential energy
the work that needs to be done by and external agent in order to bring a set of charges from where they were separated by an infinite distance to their current position
electric resistance
the ratio of the voltage across a device to the current through it
electromagnetic
an interaction mediated by the exchange of photons
electromagnetic waves
transverse waves moving at the speed of light in vacuum consisting of oscillating electric and magnetic fields at right angles to each other
electroweak interaction
the interaction that is the unification of the electromagnetic and weak nuclear interactions
elementary particles
particles that have no constituents
emf
the work done per unit charge in moving charge across the terminals of a battery
emission spectrum
the set of wavelengths of photons radiated by a substance
emissivity
the ratio of the intensity radiated by a body to the intensity radiated by a black body of the same temperature
energy density
the energy that can be obtained from a unit volume of fuel
equation of state
the equation relating pressure, volume, temperature and number of moles of a gas
equilibrium
the state when the net force on a system is zero
equipotential surfaces
set of points that have the same potential
escape velocity
the minimum speed at launch so that a particle can move to infinity and never return
exchange particle
an elementary particle used as the intermediary of an interaction
excited state
a state of energy higher than the ground state
family lepton number
a quantum number assigned to each lepton in each family
Faraday's law
the induced emf in a loop is the rate of change of magnetic flux linkage through the loop
Feynman diagram
a pictorial representation of an interaction
first harmonic
the mode of vibration of a standing wave of lowest frequency
flux linkage
the magnetic flux in a loop times the number of turns in the loop
force pair
two forces acting on different bodies that are equal and opposite according to Newton's third law
fractional uncertainty
the ratio of the absolute uncertainty to the mean value of a quantity
free-body diagram
a diagram showing a body in isolation with all forces acting on it drawn as arrows
freezing
the change from the liquid to the solid state at a specific constant temperature
frequency
the number of full oscillations or waves in unit time
fuel rods
containers of nuclear fuels in a nuclear fission reactor
full-wave recitification
the turning of ac current into dc current during both halves of the cycle
gamma ray
a photon
Note
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