Useful Physics Stuff

Front 1

to avoid ammeter affecting current

Back 1

negligible resistance
placed in series

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electrolytes

Back 2

compounds which conduct electricity when molten or aqueous (this type of conduction is called electrolysis)

Front 3

good conductor

Back 3

lots of conduction electrons that are free to move within the material
high number density
e.g copper

Front 4

good insulators

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very few or no conduction electrons, number density near to 0

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semiconductors

Back 5

intermediate properties
number densities 1,000,000 times smaller than good conductors
number density can be altered by adding a small amount of impurity to the material (doping)
low number density means conduction electrons travel much faster than in conductors
e.g silicon (used in integrated circuits)

Front 6

IV-characteristic for a thin wire

Back 6

proportional, passes through 0
I α V (at constant temperatures)

Front 7

IV-characteristic for a filament lamp

Back 7

as p.d across lamp increases, temperature of filament increases, increasing filament's resistance. starts of straight then curves outwards

Front 8

IV-characteristic of LED/Diode

Back 8

starts off along the origin then increases almost linear: ___/

Front 9

LED

Back 9

Light Emitting Diode
Diode - Allows an electric current to flow in one direction only
switch on instantly
very robust
very versatile
operate on low p.d.s
long working life

Front 10

NTC

Back 10

Negative Temperature Coefficient
increase in temperature reduces resistance
eg. all semiconductors

Front 11

LDR

Back 11

Light Dependant Resistor
large resistance when no light
low resistance with high intensity of light
can be used in street lights

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transverse waves

Back 12

direction of propagation is at right angles to the direction of the oscillations
eg. water and all em waves

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longitudinal waves

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oscillation of particles take place in the direction of propagation
regions of high pressure - compressions
regions of low pressure - rarefactions
e.g. sound waves

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progressive waves

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transfer energy from one place to another
e.g sound from a speaker to ear drums
(opposite of stationary waves)

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stationary wave

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energy is stored rather than transmitted (opposite of progressive waves)
aka standing waves

formed when two progressive waves, of the same frequency, travel in opposite directions

Front 16

intensity related to distance

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intensity α 1 / distance^2
known as the inverse square law

Front 17

intensity related to amplitude

Back 17

intensity α amplitude^2

Front 18

plane-polarised wave

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oscillates in only one plane

Front 19

uses of polarisation

Back 19

strain analysis
television transmission

Front 20

strain analysis

Back 20

certain plastics can rotate the plane of polarisation
when placed between two crossed polaroids coloured images are produced which can analyse stress.

Front 21

malus' law

Back 21

states that when a perfect polariser is placed in a polarised beam of light the intensity, I, of light that passes through it is given by:
I = I_max cos^2θ

Front 22

principle of superposition

Back 22

states that when two or more waves of the same type exist at the same place, the resultant wave will be found by adding the displacements of each individual wave

Front 23

constructive interference

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if two waves A, B exist at the same point and travel in phase, amplitude of resultant wave doubles

Front 24

destructive interference

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if two waves A,B are in antiphase, they cancel each other out, resultant has an amplitude of 0

Front 25

coherence

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constant phase difference
impossible in light waves unless waves originate from same source

Front 26

measuring wavelength of light

Back 26

use young's double slit experiement

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distance between antinodes and nodes

Back 27

quarter of a wavelength
π/2 radians

Front 28

joules to electron volts conversion

Back 28

J / 1.6x10^-19 = eV
J = eV * 1.6x10^-19

Front 29

polarisation

Back 29

only affects transverse waves

Front 30

intensity-wavelength spectrum (sun)

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high peak at the middle of violet and red

Front 31

intensity-wavelength spectrum (filament lamp)

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lower peak than sun, shifted to the right slightly
does not have dark fraunhofer lines
less emission at violet end

Front 32

spectra

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hot solids produce continuous spectra (atoms close together interfere and modify energy levels. energy levels become energy bands) - transition from one energy band to another can involve a variety of energies, hence many different wavelengths therefore continuous range of colours
hot gases produce line spectra

Front 33

absorption spectra

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when an atom absorbs energy an electron moves from a lower energy level to a higher energy level