Definitions Flashcards
What is absolute temperature?
Any temperature scale that starts at absolute zero
What is absolute zero?
The theoretical temperature at which molecules will no longer be moving, all kinetic energy has been removed
What is activity? (Radiation)
The number of radioactive decays in unit time
What is an alpha particle?
Particles compose of 2 protons and 2 neutrons, the same as a helium nucleus
What is alpha decay?
The radioactive process in which a particle of combination 2 protons and 2 neutrons is ejected from a nucleus
What is angular displacement?
The vector measurement of the angle through which something has moved
What is annihilation?
The phenomenon in which a particle and its anti-matter equivalent are both destroyed simultaneously in a conversion into energy which is carried away by force carrier particles such as photons
What is an anti-particle?
For each particle there exists and anti-particle, which has the same mass but all their other properties are opposite to those of the normal matter particle.
What is an astronomical unit?
The radius of the Earth’s orbit around the sun. 1 AU=1.5x10^11
What is atomic number?
An alternative name for proton number, the number of protons in the nucleus of an atom
What is background radiation?
Low levels of radiation from environmental sources, always present around us
What is a baryon?
A particle made of a combination of 3 quarks
What is baryon number?
The quantum number for baryons, whereby each proton or neutron (or other baryon) has a value of B=1
What is a beta particle?
An electron emitted at high speed from the nucleus when a neutron decays into a proton
What is beta-minus decay?
The radioactive process in which a nuclear neutron changes into a proton, and an electron is ejected from the nucleus
What is the Big Bang?
The theory that the universe expanded outwards, from a single point to the currently observed situation
What is the Big Crunch?
A possible future for the universe, in which it contracts inwards to a single point
What is binding energy?
The energy used to hold the nucleus together, converted from the mass deficit, following E=mc^2
What is a black body radiator?
A theoretical object that completely absorbs all radiation that lands on it
What is a black dwarf?
The final stage of the life cycle of a small mass star, when nuclear fusion has ceased and it has cooled so that it no longer emits visible light
What is a black hole?
One of the possible conclusions to the life of a large mass star; a region of space-time in which the gravity is so strong that it prevents anything from escaping including EM radiation
What is a blue supergiant?
A very large, very hot star, perhaps 25,000K
What is Boyle’s law?
Boyle’s law states that for a constant mass of gas at a constant temperature, the pressure exerted by the gas is inversely proportional to the volume it occupies
What is a bubble chamber?
A particle detection system in which the particles trigger bubbles to be created in a superheated liquid, typically hydrogen
What is capacitance?
A measure of the capability of a capacitor; the amount of charge stored per unit voltage across the capacitor. It is measured in farads, F
What is a capacitor?
An electrical circuit component that stores charge and so can be used as an energy store
What is a cathode ray?
A beam of electrons
What is centripetal acceleration?
The acceleration towards the centre of a circle that corresponds to the changes in direction to maintain an object’s circular motion
What is centripetal force?
The resultant force towards the centre of the circle to maintain an object’s circular motion
What is a chain reaction?
A self-sustaining nuclear reaction in which the products from one individual fission reaction go on to trigger one or more further fissions
What is Charles’ law?
Charles’ law states that for a constant mass of gas at a constant pressure, the volume occupied by the gas is proportional to its absolute temperature
What are control rods?
They are within a nuclear reactor and are made of materials that can absorb neutrons to stop the triggering of further fission reactions, e.g boron
What is a critically damped system?
A system where the damping is such that the oscillator returns to its equilibrium position in the quickest possible time, without going past that position
What is a cyclotron?
A circular machine that accelerated charged particles, usually following a spiral path
What are damped oscillations?
Oscillations where there is a loss in energy, reducing the amplitude over time
What is damping?
The material or system that causes energy loss during each damped oscillation
What is dark energy?
The source of a force that is causing the expansion of the Universe to accelerate; as yet its nature has not been identified
What is dark matter?
Material in the universe that explains some anomalous behaviours of celestial objects; as yet its nature has not been identified
What is decay? (Nuclear/radioactive)
A process in which the nucleus’s structure is changed, usually accompanied by the emission of a particle
What is the decay constant?
The probability, per second, a given nucleus will decay
What is the Doppler effect?
It occurs when an observer receiving waves emitted from a moving body observed that the wavelength of the waves has been altered to a new wavelength as a consequence of the relative motion
What is driving frequency?
The frequency of an external force applied to a system undergoing forced oscillations
What is an elastic collision?
A collision in which total kinetic energy is conserved
What is an electric field?
A region of space that will cause charged particles to experience a force
What are electric field lines?
Imaginary visualisations of the region of influence of an electric field
What is electric field strength?
The force to charge ratio for a charged particle experiencing a force due to an electric field
What is electromagnetic force?
One of the four fundamental forces, transmitted by photons, acting between objects with charges
What is the equation of state?
The single equation that defines a gas in terms of its pressure, volume, temperature and quantity
pV=NkT
What are equipotentials?
Positions within a field with zero potential difference between them
What are exchange bosons?
Particles that enable the transfer of force. Each of the four fundamental forces has its own exchange boson
What is an exponential curve?
A mathematical function generated by each value being proportional to the value of one variable as the index of a fixed base
f(x) = b^x
What is Faraday’s law?
Induced emf is proportional to the rate of change of flux linkage
What is fission?
When larger nuclei are broken up into small nuclides, releasing energy
What is Fleming’ left hand rule?
A system for determining the direction of the force generated by the motor effect
What is flux linkage?
The amount of magnetic flux interacting with a coil of wire.
What is a forced oscillation?
When a system oscillates under the influence of an external (usually repeatedly applied) force
What is a free oscillation?
When a system performs oscillations without any disturbance after an initial force has been applied
What is a fuel rod?
Within a nuclear reactor, and it contains the fissionable material, like U-235
What is fusion?
When small nuclides combine together to make larger nuclei; releasing energy
What are gamma rays?
High energy, high frequency, electromagnetic radiation emitted from nuclear radioactive decay
What is a gravitational field?
A region of space-time which is curved. This curvature will cause particles to experience an accelerating force
What is a graviton?
The force carrier particle (or exchange boson) for gravity
What is gravity?
The weakest of the 4 fundamental forces, transmitted by the theoretical graviton particle, affecting all objects
What is a hadron?
A particle which can interact via the strong nuclear force
What is half-life?
The time taken for half the nuclei of a sample to decay
The time taken for the activity of a sample to half
What is the Hertzsprung-Russel diagram?
A plot of stars showing luminosity (or absolute magnitude) on the y axis, and temperature (or spectral class) on the x axis
What is the Hubble constant?
The constant of proportionality in Hubble’s law
What is Hubble’s law?
The recession velocity of a galaxy is directly proportional to the distance to it
What is an ideal gas?
A theoretical gas that obeys all of the gas laws, occupies negligible space and has no intermolecular interactions
What is impulse?
The force acting for a certain time, causing a change in an object’s momentum
What is an inelastic collision?
A collision in which total kinetic energy is not conserved
What is internal energy?
The sum of all kinetic and potential energies of all the molecules within a given mass of a substance
What are isotopes?
Atoms of the same element with the same number of protons but different numbers of neutrons
What is a kaon?
A meson created from any combination of an up or down quark/anti-quark and a strange or anti-strange quark
What is kinetic theory?
The idea that consideration of the microscopic movements will predict the macroscopic behaviour of a substance
What is Lenz’s law?
The direction of an induced emf is such as to oppose the change creating it
What is lepton number?
The quantum number for leptons, whereby each lepton has a value of L = 1
What are leptons?
The six fundamental particles which do not interact using the strong nuclear force, only the other 3 fundamental forces
What is a light year?
The distance light can travel in 1 year, about 10^16
What is a linear accelerator?
A machine that accelerates charged particles along a straight line
What is luminosity?
The rate at which energy of all types is radiated by an object in all directions
What is a magnetic field?
A region of space that will cause a magnetic pole to experience a force
What is magnetic field strength?
An alternative name for magnetic flux density; the ratio of magnetic flux to the area it is passing through
What is magnetic flux?
An alternative way to refer to magnetic field lines.
It is defined as the product of the magnetic field strength and the area normal to the field
What is magnetic flux density?
The ratio of magnetic flux to the area it is passing through
What is the main sequence?
A rough diagonal line from the top left to the bottom right of a Hertzsprung-Russel diagram which marks stars that are in a generally stable phase of their existence
What is mass deficit?
The difference between the measured mass of a nucleus and the sum total of the mass of its constituent nucleons
What is the Maxwell-Boltzmann distribution?
A mathematical function that describes the distribution of energies amongst particles at a given temperature
What is a meson?
A particle made up of a combination of a quark and anti-quark
What is a moderator?
A material used in a nuclear reactor to slow fast neutrons to thermal speeds
What is the motor effect?
The phenomenon that a wire carrying current held within a magnetic field will experience a force
What is natural frequency?
The frequency of oscillation that a system will take if it undergoes free oscillations
What is neutron number?
The total number of neutrons within a given nucleus
What is a neutron star?
One of the possible conclusions to the life of a large mass star; small and very dense, composed of neutrons
What is nucleon number?
The total number of all neutrons and protons in a nucleus
What are nucleons?
Any of the protons and neutrons comprising a nucleus
What is oscillation?
The process of undertaking continuously repeated movements
What is pair production?
The phenomenon in which a particle and its anti-matter equivalent are both created simultaneously in a conversion from energy
What is a parallax angle?
The difference in angular observation of a given stat for use in the trigonometric parallax method of measuring the distance to a star
What is a parsec?
The distance the star must be from the sun n order for the parallax angle Earth-star-sun to be 1 arcsecond
1 pc = 3.09 x10^16m
What is peak current?
The maximum value, regardless of sign, of an alternating current
What is peak value?
The maximum value, regardless of sign, of a sinusoidal graph, such as that for alternating current
What is peak voltage?
The maximum voltage, regardless of sign, of an alternating current
What is the period (of a wave?)?
The time taken for one complete oscillation
What is the photoelectric effect?
A phenomenon in which electrons are released from a metal surface as a result of its exposure to EM radiation
What is a pion?
A meson created from any combination of up and down quark/anti-quark pairings
What is a planetary nebula?
The remnants of an explosion at the end of the life cycle of a low mass star; material which may eventually agglomerate into new planets
What is the plum pudding model?
A pre-1911 model of the atom in which the main body of an atom is composed of a nebulous positively charged material with electrons randomly scattered through it
What are magnetic poles?
The magnetic equivalent of charge on a particle, can be north or south
What is potential?
A measure of possible field energy in a given location within that field. Electric potential is the energy per unit charge at that location
What is potential difference?
A change in potential between two locations in a given field
What is pressure law?
For a constant mass of gas at a constant volume, the pressure exerted is proportional to the absolute temperature
What is a primary coil?
The first coil in a transformer, in which the supply current passes
What is proton number?
The number of protons in the nucleus of an atom?
What is a protostar?
Dust and gas clumping together under the force of gravity, prior to the start of nuclear fusion in its core, which will go on to become a star
What are quarks?
The six fundamental particles that interact with each other using the strong nuclear force
What is a radian?
A unit of angle measurement, equivalent to 57.3°
What is a red giant?
A large star, somewhat cooler than our sun e.g. 3000K
What is red shift?
The shift in wavelength of a star’s spectrum, caused by increasing separation between the star and the Earth
What is resonance?
Very large amplitude oscillations that occur when a driving frequency matches the natural frequency of a system
What is root-mean-square speed?
The square root of the arithmetic mean value of the squares of the speeds of particles in an ideal gas
What is a secondary coil?
The second coil in a transformer, in which the output current passes
What is simple harmonic motion?
When a system is oscillating such that a force is trying to return the object to its centre position, and this force is proportional to the distance from that centre position
What is specific heat capacity?
The energy required to raise the temperature of 1kg of a substance by 1°
What is specific latent heat?
The energy required to change the state of 1kg of a substance at constant temperature
What are standard candles?
Stars with properties which mean their luminosity can be determined from measurements of brightness i.e. stars of known luminosity
What is the standard model?
The name given to the theory of all the fundamental particles and how they interact. This is the theory that currently has the strongest experimental evidence
What is the Stefan-Boltzmann law?
The power output from a black body is proportional to its surface area and the fourth power of its temperature in Kelvin (L = σAT^4)
What is strangeness?
The quantum number for strange quarks, whereby each has a value of S = -1
What is the strong nuclear force?
The extremely short range force between hadrons (such as protons and neutrons)
What is a supernova?
The explosion of a large mass star at the end of its lifetime when it becomes extremely unstable
What is a synchrotron?
A machine that accelerates charged particles around a fixed circular path
What is tesla (T)?
The unit for magnetic flux density, or magnetic field strength
What is a thermal neutron?
A relatively slow moving neutron
What is thermionic emission?
The phenomenon in which electrons are released from a metal surface as a result of its exposure to thermal energy
What is time constant?
For a capacitor-resistor circuit, the product of the capacitance and resistance, giving a measure of the rate for charging and discharging the capacitor, symbol τ
What is trigonometric parallax?
A method for measuring the distance of relatively close stars. It works by comparing their measured angle in the sky at six monthly intervals, and using these measurements to calculate the distance using trigonometry
What is the weak nuclear force?
One of the four fundamental forces, transmitted by W or Z bosons, acting at extremely short ranges (10^-18m); it can affect all matter particles
What are Webers (Wb)?
The unit of measurement of magnetic flux (φ) (and magnetic flux linkage Nφ)
What are Weber-turns?
The unit for magnetic flux linkage
What is a white dwarf?
A small, hot star, perhaps 10,000K
What is Wien’s law?
The relationship between peak output wavelength and temperature for a black body radiator is given by the equation λmax x T = 2.898x10^-3 m K)
