# Physics

- Created by: Paddy Denny
- Created on: 14-12-12 17:44

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- Physics
- Imaging
- Pixels
- Resolution= Distance / No. of Pixels

- Digital
- 1 bit - Smallest amount of information (0 or 1)
- 1 byte = 8 bits
- If 'I' is the number of bits
- 2^I is the number of alternatives

- To find number of bits log2(No. of choices needed)

- Uses Binary
- No. of Alternatives = 2

- 1 bit - Smallest amount of information (0 or 1)
- No. of bits per image
- No. of pixels x No. of bits needed for colour scheme
- No. of bytes = No. of bits / 8

- No. of pixels x No. of bits needed for colour scheme
- Coloured Images
- Red + Green
- Yellow

- Red + Blue
- Purple

- Blue + Green
- Syan (Turquoise)

- Red + Blue + Green
- White

- Red + Green
- Finding Edges
- Laplace Kernel
- 4
- 0
- -1
- 0
- 0
- 0
- -1
- -1
- -1

- Negative values become 0

- 4

- Laplace Kernel
- Smoothing
- Median - replace with median of surrounding values
- Mean - Replace with mean of surrounding squares

- Pixels
- Testing Materials
- Young's Modulus
- Stress (Nm-1) = Force (N) / Area (m2)
- YM (Pa) = Stress (Pa) / Strain
- Strain = Extension (m) / Orig. Length (m)

- Types of materials
- Ceramic
- Electrical Insulator
- Plastic
- Often Malleable
- Can be tough
- Can be hard
- Ductile

- Plastic
- Brittle
- Readily cracks on impact or shock

- Thermal Insulator
- Plastic
- Often Malleable
- Can be tough
- Can be hard
- Ductile

- Plastic
- Hard

- Electrical Insulator
- Metals
- Tough
- Can withstand large shocks or impacts before breaking

- Sonorous
- Hard
- Does not easily scratch

- Electrical Conductor
- Strong
- Can withstand high stress before yield or fracture

- Thermal conductor
- Malleable
- Can be hammered into sheets

- Ductile
- Can be drawn out into a wire

- Tough

- Ceramic
- Resistance = Resistivity x Length / Area
- Hooke's Law
- Stretching Force (N) =Spring Constant (Nm-1) x Extension (m)
- Only applies up to the elastic limit

- Conductance = Conductivity x Area / Length

- Young's Modulus
- Signalling
- Digital
- 1 bit - Smallest amount of information (0 or 1)
- 1 byte = 8 bits
- If 'I' is the number of bits
- 2^I is the number of alternatives

- To find number of bits log2(No. of choices needed)

- Uses Binary
- No. of Alternatives = 2

- 1 bit - Smallest amount of information (0 or 1)
- Sampling Frequency
- At every sampling frequency round to nearest value
- Convert each point sampled on curve to binary
- Draw in bursts digital on/off graph

- Convert each point sampled on curve to binary
- Sampling Frequency must be at least 2x highest frequency
- Highest Frequency - W (Hz)=1/T(s)

- At every sampling frequency round to nearest value
- Digitizing a Signal
- At every sampling frequency round to nearest value
- Convert each point sampled on curve to binary
- Draw in bursts digital on/off graph

- Convert each point sampled on curve to binary

- At every sampling frequency round to nearest value
- No. of levels needed
- V-Signal (V) / V-Noise (V)
- No. of bits = log2(No. of levels)

- Velocity = Frequency x Wavelength
- Transmission Rate
- Sampling Frequency x No. of Bits
- 2W log2 ( V-signal / V-noise)
- Sampling Frequency x No. of Bits

- Transmitting Waves
- Digital
- Amplitude Modulated or Frequency Modulated

- Analogue
- Amplitude Modulated

- Digital
- Wave View
- Amplitude same
- Frequency View
- Frequency on x-axis

- Frequency View
- Frequency = 1/T

- Amplitude same
- Frequency View
- Frequency on x-axis

- Polarisation

- Digital
- Looking Inside Materials
- Internal Structure
- Crystalline rows of ions in a strict order
- Polycrystalline - A structure made up of many interlocking crystals with grain boundaries.
- Amorphous - Random atoms and molecules in no order

- Bonding in materials
- Metallic - non directional
- Ionic - Non directional
- Covalent - Directional

- Alloys
- Impurities pin dislocatioons so they cannot move through the whole crystal.

- Metals
- Sea of electrons allows positive ions to just slip past each other
- Ductile
- Can be drawn out into a wire

- Ductile

- Sea of electrons allows positive ions to just slip past each other

- Internal Structure
- Sensing
- Types of Resistor
- Resistance increases with voltage as temperature increases
- Resistance calculated by taking spot values

- Ohmic Resistor
- Ratio of V/I is a constant
- Resistance is the constant

- Ratio of V/I is a constant

- Resistance increases with voltage as temperature increases
- Resistors
- Series
- Rt = R1+R2
- I1=I2=I3
- Vt=V1+V2

- Parallel
- 1/Rt = 1/R1 +1/R2
- Rt = R1R2/R1+R2
- Iseries = Ipara1+ Ipara2
- V=V of battery

- Series
- Semiconductors
- LDR, Diode, Thermistor
- In a potential divider circuit
- V of LDR/ V of Ohmic Resistor = R of LDR/R of Ohmic Resistor
- Sensing Circuit
- Sensitivity = Change in Output/Change in Input
- For LDR: Change in PD/Change in distance
- Gradient

- Resolution
- Smallest detectable change in input
- Precision / Sensitivity

- Sensing
- Types of Resistor
- Resistance increases with voltage as temperature increases
- Resistance calculated by taking spot values

- Ohmic Resistor
- Ratio of V/I is a constant
- Resistance is the constant

- Ratio of V/I is a constant

- Resistance increases with voltage as temperature increases
- Resistors
- Series
- Rt = R1+R2
- I1=I2=I3
- Vt=V1+V2

- Parallel
- 1/Rt = 1/R1 +1/R2
- Rt = R1R2/R1+R2
- Iseries = Ipara1+ Ipara2
- V=V of battery

- Series
- Semiconductors
- LDR, Diode, Thermistor
- In a potential divider circuit
- V of LDR/ V of Ohmic Resistor = R of LDR/R of Ohmic Resistor
- Sensing Circuit
- Sensitivity = Change in Output/Change in Input
- For LDR: Change in PD/Change in distance
- Gradient

- Resolution
- Smallest detectable change in input
- Precision / Sensitivity

- Sensitivity = Change in Output/Change in Input

- In a potential divider circuit
- Diodes have forward and reverse bias, current can only flow one way

- LDR, Diode, Thermistor
- Potential Divider
- V1/V2 = R1/R2

- EMF and internal resistance
- E=V+Ir

- Improving a circuit
- 2 semiconductor sensors cancels out effect of other factors

- Equations
- I=Q/t
- V=W/Q
- W=ItV
- R=V/I
- R=pL/A
- P=W/t
- P=IV
- E=Pt

- P=IV

- P=W/t

- R=pL/A

- R=V/I

- W=ItV

- V=W/Q

- I=Q/t

- Types of Resistor

- Sensitivity = Change in Output/Change in Input

- In a potential divider circuit
- Diodes have forward and reverse bias, current can only flow one way

- LDR, Diode, Thermistor
- Potential Divider
- V1/V2 = R1/R2

- EMF and internal resistance
- E=V+Ir

- Improving a circuit
- 2 semiconductor sensors cancels out effect of other factors

- Equations
- I=Q/t
- V=W/Q
- W=ItV
- R=V/I
- R=pL/A
- P=W/t
- P=IV
- E=Pt

- P=IV

- P=W/t

- R=pL/A

- R=V/I

- W=ItV

- V=W/Q

- I=Q/t

- Types of Resistor

- Imaging

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