OCR B Advancing Physics AS Unit 1

Key words/ and definitions. Equations and any notes. Most thing is on there - not randomised. Some may be muddled about. Wikibooks have a printible copy of this with images.

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  • Created by: Yamuna
  • Created on: 30-12-12 17:32
Rate of transmission of digital information
sample per second X bits per scample
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Maximum rate of sample
2 X maximum frequency of signal
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Amount of information of an image
No. of Pixels X bits per pixel
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Current
A flow of charged particles
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Potential Difference
Energy/ Charge
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Stress
Force/ Cross Sectional Area. Measured in Pa
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Strain
Extension/ Original Length . No units.
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Young Modulus
Stress/ Strain .
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Tensile Strength / Fracture Stress
The level of stress at which a material will fracture. If the material fractures by 'Crack Propogation' then the material is brittle.
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Yield Stress / Yield Strength
The level of stress at which a material will deform permanently.
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Elastic Region
The region where the ratio of stress to strain is constant.Material here is obeying Hooke's Law.On a graph will be represented as a directly proportional line.
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Hooke's Law
This Law states that the Force (load) is directly proportional with the extension of a material as long as the load does not exceed the elastic limit.
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Deformation
The change in an objects shape or size due to stress
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Elastic Deformation
The temporary change in the shape of an object as a result of stress. Once the stress is removed, the object returns to its original shape.
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Plastic Deformation
Deformation that is permanent. Plastic deformation occurs after excessive elastic deformation.
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Yeilding
The slow deformation of a material over time. Also known as creep.
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Metals
A solid material that is typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivity.
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Ceramics
Any non-metallic solid that remains hard when heated
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Polymer
A substance that has a molecular structure consisting chiefly or entirely of a large number of similar units bonded together, e.g., many synthetic organic materials used as plastics and resins. Basically a molecular chain made up of single repea
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Glasses
A hard, brittle substance, typically transparent or translucent, made by fusing sand with soda, lime, and sometimes other ingredients and cooling rapidly.Any similar substance that has solidified from a molten state without crystallizing
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Composites
A material that is made up of more than one different types of materials chemically bonded together, to get desirable properties.
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Tough
Toughness is a measure of the energy a material can absorb before it breaks.
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Brittle
When a material breaks suddenly without deforming plastically.
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Elastic
An object or material that is able to resume its normal shape spontaneously after contraction, dilatation, or distortion .
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Plastic
A material that can deform but will not return to its original shape once the deforming force has been removed.
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Flexible
A material that will modify itself to respond to a change of condition.
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Strong
A materials ability withstand great force or pressure.
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Ductile
Ductile materials can be drawn out into wire.
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Hard
Hard materials are resistant to cutting, indentation and abrasion
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Soft
A material that is easy to mould, cut, compress, or fold; not hard or firm to the touch.
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Malleable
Malleable materials are able to change shape but has the potential to loose strength.
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Stiff
Have a high resistance to bending and stretching.
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Metal Properties
Metals have a structure that allows electrons to move through it, conducting an electric current.Force of attraction allows it to be stiff.
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Polymer- Transparency
Polymers that are crystalline are usually opaque.Polymer become less poly crystalline they become transparent.
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Polymer - Elasticity
polythene, the chains are folded up. When stretched, the chains unravel, stretching without breaking. When the stress ceases, they will return to their original shape. If, however, the bonds between the molecules are broken, they don't return.
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Polymer- Stiffness
Polymer chains may be linked together, causing the polymer to become stiffer. An example is rubber, which, when heated with sulfur, undergoes a process known as vulcanization.Stiffer polymers are more brittle.
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Polymer-Placticity
When a polymer is stretched, the chains become parallel, and amorphous areas may become crystalline. This causes an apparent change in colour, and a process known as 'necking'.
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Polymer - Conductivity
Polymers consist of covalent bonds, so the electrons are not free to move according to potential difference. This means that polymers are poor conductors.
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Boiling point
Polymers do not have boiling points. This is because, before they reach a theoretical boiling point, polymers decompose. Polymers do not have melting points for the same reason.
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Ohm's Law - V=IR
Ohm's Law states that the potential difference across an artefact constructed from Ohmic conductors is equal to the product of the current running through the component and the resistance of the component
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Internal Resistance
The existence of internal resistance is indicated by measuring the potential difference across a battery. This is always less than the EMF of the battery. This is because of the internal resistance of the battery.
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Properties of Sensors
You need to know about the sensitivity , resolution and response time.
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Resistivity
Resistivity is- Resistance X Cross Sectional Area / Length
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Conductivity
Conductivity is - Conductance X Length/ Cross Sectional Area
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Semiconductors
They are less conductive than metals, but differ from metals in that, as a semiconductor heats up, its conductivity rises.Very few atoms are ionised, very few electrons can move, creating an electric current. When heated, covalent bonds broken.
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Power
P= E/t= IV P=I^2R P=V^2/R P= QV/t
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Votage
V=E/Q
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Electromotive Force ( EMF)
The potential difference across the terminals when the key is open i.e. when no current is drawn from the cell
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Current
Charge/ time or symbol equation. Q/t where Q= Charge and t= time in seconds
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Charge
N=Q/q. Where N= number of particles, Q= Total Charge and q= charge of particles.
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Frequency Equation
Velocity of wave= frequency of wave X wavelength. The fundamental frequency is the lowest frequency that makes up a signal.
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Sampling Rate
No. of samples/No. of seconds.
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Mean Smoothing
The fundamental frequency is the lowest frequency that makes up a signal.Does not remove noise ,blurs image.
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Median Smoothing
A far better method is, instead of taking the mean, to take the median.
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Edge detection
We can detect the positioning of edges in an image using the 'Laplace rule', or 'Laplace kernel'. For each pixel in the image, we multiply its value by 4, and then subtract the values of the pixels above , below it, east and west of it.treat -ve as 0
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Bytes
8 bits equal a byte.
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Sampling limited by noise
Maximum bits per a sample limited by log^2(v total/v noise)
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Magnification
m= v/u where v and u equal image and object distance.
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Converging Lens
Converging lenses add curvature to the wavefronts, causing them to converge more. These have a positive power, and have a curved surface which is wider in the middle than at the rim.
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Diverging Lens
Diverging lenses remove curvature from the wavefronts, causing them to diverge more. These have a negative power, and have a curved surface with a dip in the middle.
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Lens Equation
1/V =1/u + 1/f
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Power of lens
P= 1/f
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Curvature of wavefront
C= 1/v with C = Curvature and v= distance from wavefront.
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Card 2

Front

2 X maximum frequency of signal

Back

Maximum rate of sample

Card 3

Front

No. of Pixels X bits per pixel

Back

Preview of the back of card 3

Card 4

Front

A flow of charged particles

Back

Preview of the back of card 4

Card 5

Front

Energy/ Charge

Back

Preview of the back of card 5
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