# Physics - Unit 1

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• Created by: Geot
• Created on: 23-05-14 11:28
• Physics - Unit 1
• 1. Energy Transfer
• 1.1: Infrared Radiation - Heat energy transfer by electromagnetic waves; emitted by all objects; direct correlation of heat with emitted infrared radiation.
• 1.2: Surfaces and Radiation - Dark, matt surfaces emit and absorb more radiation/heat than light, shiny surfaces; lighter surfaces reflect more radiation.
• 1.3: States of Matter - Flowe, shape, volume and density are used to define states of matter; particles in a solid are connected and fixed; particles in a liquid are connected and fluid; particles in a gas are unnconected and free-moving.
• NOTE: CATS ARE A LIQUID!
• 1.4: Conduction - Metals are the best conductors of energy (ALL ENERGY - NOT JUST ELECTRICITY) as they have fixed structures and free electrons; non-metals such as wool and fibreglass are the best insulators as they do not contain free electrons.
• 1.5: Convection - circulation of a fluid (liquid or gas) by heating it; heat makes it less dense, causing it to rise and cool.
• 1.6: Evaporation and Condensation - Liquid into gas; gas into liquid; cooling by evaporation is due to fast moving molecules are released.
• NOTE: Earth's water cycle is a continous example of evapouration and condensation. Ocean -evapouration-> Cloud/Cloud -condensation-> Rain/Rain -precipitation-> Surface water/SW - run-off-> Ocean
• 1.7: Energy transfer by design - Rate of energy transferred depends on size, shape, volume, SA, material, contacting materials, delta temperature between the object and surroundings.
• 1.8: Specific Heat Capacity - The greater mass of an object, the slower its temperature increases; the delta temperature depends on: energy supplied, mass, and shc.
• NOTE: Typical specific heat capacities - Water: 4.2 J/g/degrees C, Ethanol: 2.5, Copper: 3.85, Diesel: 2.05
• 1.9: Heating and Insulating buildings - Energy transfer can be controlled by: loft insulation, wall cavity insulation, double glazing, draught excludeds; U-values (E/s that passes through 1m sq when Delta temp°C is 1°C) can be used to compare materials - the lower the U-value, the more effective the material is as an insulator.
• 2. Using Energy
• 2.1:  Forms of Energy - Energy exists in different forms (Chemical, Kinetic, Potential); it can change from one to another; when an object falls, the grav potential decreases and the kinetic energy increases.
• NOTE: The most common forms of energy are - Thermal (Infrared, Heat), Kinetic (Movement), Potential (Gravity), Chemical (Electrochemical), Sound, Friction, Elastic,  Electrical, Electromagnetic, Nuclear.
• 2.2: Conservation of Energy - ENERGY CANNOT BE CREATED OR DESTROYED, JUST TRANSFORMED; conservation applies to all ordinary energy changes.
• 2.3: Useful Energy - Useful energy is energy in the correct place and form that is required; any lost energy is wasted; both useful and wasted energy are transferred to the surroundings WHICH WILL ALWAYS HEAT THE SURRONDINGS, REGARDLESS OF FORM.
• 2.4: Energy and Efficiency - The efficiency of a device = useful energy/total energy supplied in %; No machine can be more than 100% efficient; measures to make machines more efficient include reducing friction, drag, resistance., etc.
• 3. Electrical Energy
• 3.1: Electrical Appliances - Appliances can transfer electrical energy into useful energy; everyday uses include heating, lighting, creating light, sound, and movement.
• 3.2: Electrical Power - Power is the rate of energy transfer, measured in Watts (W), Kilowatts (KW) or Megawatts (MW); P = E/time.
• NOTE; WATTS are just measures of power. KILOWATT HOURS is a measure of energy supplied, allowing the Big Six to overcharge us.
• 3.3: Using Electrical Energy - A kilowatt-hour is the energy supplied to a kilowatt appliance in one hour - although not all appliances are 1 kilowatt exactly; E = P x time; total cost = no. kWh x cost per kWh.
• 3.4: Cost effectiveness matters - CE means getting the best value for money out of something - this is dependent on material, quality, production costs and transport; running costs and environmental costs are also dependent on the Green Energy rating of an appliance.
• 4. Generating Electricity
• 4.1: Fuel for Electricity - Electricity generators are driven by steam turbines; coal, oil and natural gas are the three most common burned in power stations; Uranium or Plutonium are used in nuclear power; biofuels include Methane (CH4) and Ethanol (C2H5OH)
• 4.2: Wind, Tidal and Hydropower - Wind turbines capture wind energy (and unfortunate birds) and convert it into power; wave generators are floating generators powered by the movement of the waves; hydroelectricity generators are turned by water freefall through the inside of a dam, turning the generator; tidal power stations trap tidal surges and gradually release it again, generating power.
• 4.3: Solar and Geothermal - Solar cells are flat solid cells that convert light energy directly into electricity; solar heating panels use the Sol's heat to heat water; geothermal energy comes from energy released by reactions deep within Earth - water pumped onto hot rocks underground produces steam to drive the turbines.
• NOTE: Iceland are the world's largest supplier of geothermal energy, thanks to their island being situated directly on top of the Mid-Atlantic Ridge.
• 4.4: Energy and the Environment - Fossil fuels produce increased levels of greenhouse gases (400 ppm or 0.04 %), which destroys the ozone and can cause global warming; nuclear fuels produce no emissions other than radioactive waste; renewable energy resources can have a devastating effect on plant and animal life.
• NOTE: The most infamous nuclear disaster of all time is when Reactor No. 4 in Chernobyl went into meltdown and exploded killing 31 people, irradiating thousands of others and making the surrounding area uninhabitable for the next 20,000 years. More recently, the Japanese Tohoku earthquake and tsunami caused three of the six reactors at Fukishima nuclear plant to also go into meltdown.
• 4.5: The National Grid - the National Grid is a network of power plants, control stations, cables and transformers across the UK that distribute and control both fossil and renewable energy to the country; step-up transformers are used to increase voltage from power stations to grid levels, and step-downs are used to decrease the voltage into the mains; a high grid voltage reduces energy loss and makes the system more efficient.
• NOTE: Countries which rely more and more on green energy have weaker, less reliable grids; due to the fact that most green energy is temperamental.
• 4.6: Energy issues - Gas-fired power stations can meet variations in demand when and where needed; nuclear, coal and oil can meet base-load demands; whilst wind, solar, tidal and to an extent, geothermal, cannot.
• 5. Waves
• 5.1: The Nature of Waves - Waves are used to transfer energy and information.; transverse waves vibrate at right-angles to the direction of energy transfer; longitudinal waves vibrate parallel to the direction of energy transfer; mechanical waves, which need a medium to travel through, may be t-waves or l-waves.
• NOTE: All electromagnetic waves are transverse.
• NOTE: Sound waves are an example of longitudinal waves
• 5.2: Measuring Waves - For any wave - its amplitude is the height of the wave crest/trough from 0; its frequency is the no. of crests passing a point in one second; its wavelength is the s from one crest/trough to the next.
• 5.3: Reflection - For a light ray to be reflected by a mirror: the angle of incidence must be between the incidence ray and the normal; the angel of reflection must be between the ray and the normal; the law of reflection states that the angle of incidence = the angle of reflection.
• 5.4: Refraction - 'the change of direction of waves when they cross a boundary into a different density;' when a light ray refracts as it travels from air into glass, the angle of refraction is less than the angle of incidence; when a light ray refracts as it ravels from glass to air, the angle of refraction is greater than the angle of incidence.
• 5.5: Diffraction - 'the spreading of waves when they pass through a narrower gap, or around an obstacle;' the narrower the gap is, the greater the diffraction is; if radio waves do not diffract enough, radio and TV reception will be poor.
• 5.6: Sound - Human hearing ranges from 20 Hz to 20,000 Hz (the upper limit decreases with age); sound waves are vibrations that travel through a medium. They cannot travel a vacuum (eg. space); echoes are due to sound waves being reflected by smooth, hard surfaces.
• 5.6: Pitch - The pitch of a note increases if the frequency of the sound waves increases; the volume of a note increases if the amplitude increases; vibrations created in an instrument when it is played produces sound waves.
• NOTE: Different instruments achieve vibration by different means: strings by the bow and string, wind by the reeds, brass by the mouthpiece.
• 6. Electromagnetic Waves
• 6.1: The Electromagnetic Spectrum - Waves of different lengths, across the spectrum; the wave speed equation is used to calculate the frequency or wavelength of electromagnetic waves.
• NOTE: In order of longest to shortest wavelengths - radio, micro, infrared, light, ultraviolet, gamma, X-rays.
• 6.2 - Light, Infrared, Microwaves and Radio Waves - White light contains all the colours of the visible spectrum; Infrared is used for carrying signals from remotes and optical fibres, microwaves carry satellite TV and mobile phone connections, radio waves are for TV broadcasting, radio comms and WiFi.
• NOTE: Different types of electromagnetic radiation are hazardous - microwaves can cause internal heating whilst UV can cause skin burns.
• 6.3: Communications - Radio waves of different frequencies are used for different purposes as wavelength affects reach, spread, speed and amount carried; further research is needed to evaluate rumours of whether mobile phones are safe to use; optical fibres are very thin wires used to transmit signals by light and infrared radiation.
• NOTE: Optical fibres are very useful as they can transmit multiple signals at once along the same 'wire' as long as all signals are at a different angle under 84 degrees, to a minimum of 0.1 degree.
• 6.4: The  (Increasingly) Expanding Universe - Red-shift is the shift to longer wavelengths of light, useful for calculating the distance and speed of galaxies and clusters around us; the greater the red-shift, the faster the galaxy/body is moving away from us.
• NOTE: All galaxies and clusters are moving away from each other because the Universe is expanding. The rate of expansion has recently increased - and no-one knows why (DUHN-DUHN-DUHN!).
• 6.5: The Big Bang - The Universe began with The Big Bang from an infinitesimally small point known as The Singularity; it has been expanding ever since; C(osmic) M(icrowave) B(ackground) R(adiation) is electromagnetic radiation created just after the Big Bang, allowing us to date it to 13.8 billion years; CMBR is the definitive proof of The Big Bang as there is no other way for it to have been created.
• NOTE: The Big Bang was not so much an explosion as a sudden and colossal inflation of The Point or Singularity over the first few seconds of The Universe.
• BANG!
• NOTE: The Big Bang was not so much an explosion as a sudden and colossal inflation of The Point or Singularity over the first few seconds of The Universe.