AQA A level Physics Paper 1

Current Rate of flow of charge Coulomb The amount of charge passing a point when a current of 1A flows for 1s 00:11 01:10 Potential difference The work done per unit charge in moving a small point positive charge between two points Threshold Voltage for a Diode The voltage at which a current will begin to flow at, assumed to be +0.6V if not stated Reverse Bias When very little currency can flow in the reverse direction of a diode Variable Resistor Can be used to change the current through a circuit can also be called a rheostat NTC Thermistor (A type of semiconductor) that has decreasing resistance when its temperature increases - negative temperature coefficient Transitional Temperature The critical temperature at and below which a superconductor has zero resistivity Semiconductor A group of materials which conduct electricity (not as well as metals), when their temperature rises they can release more charge carriers and their resistance decreases Resistance The ratio of a components potential difference to its current Volt The potential difference across a component when 1 joule of energy is used to move a coulomb of charge through a component Ohm's Law Provided that the physical conditions remain the same, the current through an ohmic conductor is directly proportional to the potential difference across it Ohmic conductor A material that follows Ohm's law when physical components remain the same Diodes Components made from semi conductors that only allow current to flow in one direction Resistivity The resistance of a 1m length of wire with a 1m^2 cross sectional area Superconductor A material that has zero resistivity when it is cooled below its critical temperature Critical Temperature The temperature below which a material will have zero resistance and will become a superconductor Power The rate of transfer of energy EMF The work done in moving a unit charge through a battery Lost Volts Work done per unit charge in overcoming the internal resistance within a battery Terminal PD The potential difference between the two terminals of the power supply Potential Divider A circuit with a constant voltage source and more than one resistor connected in series that can be used to vary the output voltage Threshold Frequency The minimum frequency that must be incident on the surface of a metal for the emission of photoelectrons to occur Electromagnetic Force A fundamental force that causes interactions between charged particules. Virtual photons are the exchange particles Gravitational Force A fundamental force which causes attraction between objects with a force proportional to their mass Strong Nuclear Force A fundamental force with a short range which is attractive between 0.5-3 fm and repulsive between 0-0.5fm Alpha Decay Occurs in nuclei of 82 protons or more that consists of an alpha particle being emitted Photons Virtual particles that are discrete packets of energy Antiparticle Opposite in charge to the particle but have the same rest mass and rest energy PET Scan Positron Emission Tomography Rest Energy The amount of energy that would be produced if all of a particle's mass was transformed into energy Fundamental Particle A particle that cannot be split up into smaller particles Stopping Potential The work done by the potential difference in stopping the fastest moving electrons Electron Volt The kinetic energy that an electron has after being accelerated from rest through a potential difference of 1 volt 1 eV = 1.6x10^-19 Joules Ground State The lowest energy level that an electron can occupy in an atom (n=1) Excitation When an electron gains the exact amount of energy needed to move up to a higher energy level in an atom Ionisation The process when an electron gains enough energy from a photon to leave the ground state of the atom that it's in Ionisation Energy The amount of energy needed to remove an electron from the ground state of an atom Radian The angle that is equal to the arc length divided by the radius of the circle 2pi radians = 360 degrees Angular Speed The angle an object rotated through per second (omega = 2pi x frequency) Frequency The number of complete revolutions per second Light Damping Stops oscillations over many time periods (just air resistance etc) Heavy Damping Stops oscillations in few time periods, amplitude gets much smaller each period (like adding a parachute or something)