Definitions For Edexcel AS Physics

Just what it says in the title really. It's not split up into Unit 1 and Unit 2 - it is alphabetical though. Also, I'd like to point out that these may not be definitions that are guarenteed to get you full marks in the exam - for example, I use the word "light" in the definition of "plane polarised light", but in one exam you had to specify that light was electromagnetic radiation to get all the marks. Stuff like that my occasionally crop up, so in the exam, look to see how many marks are for the definition and try to make as many separate points as there are marks, and don't blame me if my definitions weren't quite as accurate as needed (they are all correct though). If you spot any missing, just comment and I'll endeavour to put them in.

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Acceleration The rate of change of velocity with respect to time (a= v/t)
Ammeter A device used to measure electric current in a circuit, connected in series.
Assumed to have negligible resistance.
Ampere SI unit for electric current (rate of flow of charge)
Amplitude The maximum displacement of a wave from its rest/mean position
(measured in metres)
Antinode A point of maximum amplitude along a stationary wave caused by
constructive interference
Brittle A material is brittle if it will shatter or break easily if subjected to shocks
or impacts
Coherence Waves are coherent if they have the same wavelength, frequency and
maintain a constant phase relationship
Critical angle The angle of incidence such that the angle of refraction is 90°
Displacement The vector quantity of the distance of an object from its initial position
Diffraction The spreading of a wave as it passes through a gap. Smaller gap more
diffraction; long wavelength more diffraction
Density The mass of a body per unit volume
Doppler effect The change in the frequency a wave detected by an observer due to the
relative motion of the source of that wave to the observer
Drift Velocity The speed at which electrons flow through a wire (I=nAqV; I=current;
n=electron density; A=cross-sectional area; q=electron charge; v=drift
Ductile A material is ductile if it can be drawn into wires
Elastic A material is elastic if it regains its original dimensions when the
deforming force is removed
Elastic Deformation that is reversed when the deforming force is removed
Energy The stored ability to do work
Energy Level A discrete amount of energy associated with an electron orbit around an
Extension The change in the length of an object when a force is applied to it
Electromotive The maximum potential that a cell has ( =IR+Ir; IR=voltage in circuit;
Force (e.m.f.) Ir="lost volts" due to internal resistance)
Force A force causes a mass to change motion (F=ma)
Frequency The number of waves that pass a fixed point in a unit of time

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Gravitational The energy an object has due to its relative position above the ground
Potential Energy ( GPE=mg H)
Hard A material is hard if it is difficult to indent or scratch the surface
Hooke's Law The extension of a spring is in direct proportion with load added to it (F=k
Hysteresis The difference between the work done on a material during an action and
that action's opposite (e.g.…read more

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Phase Waves are in phase if they have the same frequency and wavelength, and
identical points line up exactly (e.g. troughs of wave 1 line up with the
troughs of wave 2). Waves are out of phase by an angle - 180 (or
radians) out of phase means that wave 1 is half a wavelength behind wave 2
(i.e.…read more

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Thermistor A resistor that changes its resistance depending on its temperature
(usually temperature increase resistance decrease)
Threshold The lowest frequency of electromagnetic radiation that will result in the
Frequency emission of photoelectrons from a specified metal surface (E=hf)
Total internal The complete reflection of a light wave due to its angle of incidence being
reflection greater than the critical angle, so the angle of refraction is >90°, meaning
the light bounces back
Transverse wave A wave that transfers energy as a result of oscillations/vibrations that…read more

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Coulomb (C) Unit of charge (Q)
Electronvolt (eV) The energy given to one electron when it passes through a potential
difference of one volt (1 eV = 1.6x10-19 J)
Joule (J) The SI unit of work done, or energy. It is the work done when a force of 1
newton moves an object 1 metre
Newton (N) Unit of force.…read more



Brittle should be:

A material is Brittle if, when undergoing a tensile force, there is little or no plastic deformation.

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