Physics P1

1. Form of electromagnetic wave
2. Emitted by all objects
3. Detected as heat

1. Black matt surfaces both emit and absorb IR the best
2. White shiny surfaces are the worst absorbers and emitters of IR

1. Solid
   1. Particles in uniform format, vibrating in a fixed position
2. Liquid
   1. Particles move about at random
   2. Still in contact with each other
3. Gas
   1. Move about randomly with high kinetic energy
   2. Particles much further apart and not in contact

1. Conduction in Metals
   1. Metals are best conductors
   2. Delocalised free electrons transfer vibration down the material by colluding with the other particles
2. Insulator- Poor conductor
3. Particles near the heat source gain kinetic energy and vibrate more. This movement is passed on to neighbouring particles

1. Occurs in fluids
2. Heating causes the fluid to become less dense, therefore it rises and is replaced by the cooler particles
   1. Causes convection currrent

1. Evaporation
   1. When a liquid turns into a gas
   2. Particles with the highest kinetic energy escape, taking energy with it, causing cooling
   3. Rate increased by
      1. Increasing surface area of liquid
      2. increasing temperature of liquid
      3. Draught across surface
2. Condensation
   1. When gas turns to liquid
   2. Rate increased by
      1. Increasing surface area
      2. Reducing surface temperature

1. Heat goes from hot to cold
   1. Greater the temperature difference between object and surroundings, wuicker energy is transfered
2. Maximise transfer
   1. Use good conductors
   2. Matt black
   3. Air flow
3. Minimise transfer
   1. Use of insulators
   2. White and shiny
   3. Trapped air

1. Energy required to heat 1kg of a substance by 1 degree
   1. Greater mass more energy needed
2. E=mass x SHC x temp. change
3. J/kg(o)C

Anotações:

• Light Sound Kinetic Thermal Nuclear Gravitational Potential Elastic Potential Magnetic Electrical Chemical

1. Transferred from one type to another

1. Energy cannot be created or destroyed
2. Total energy always the same

1. Useful Energy- Transferred where and in the form we want
2. Wasted Energy- Not useful energy
3. All eventually transferred to surroundings, making it harder to use

1. Efficiency= (Useful energy/ Total energy supplied) x100
2. Can't be more than 100% efficient
3. Represented in Sankey diagram

1. Transfers electricity into any useful form
2. Should waste as little energy as possible

1. Power- Rate it transfers energy
   1. Watt
      1. 1kW=1000W
2. Power= Energy/ Time

1. Kilowatt-hour- Energy transferred to kW appliance in an hour
2. Energy= Power x Time
   1. kw=kW x h
3. Total cost= Number of kWh x Cost per kWh

1. Best value for money
2. Payback Time- Time for appliance to save same as it cost
   1. Payback Time= Cost/ Saving per year

1. Fossil fuel burnt to turn wter to steam
2. Steam turn turbine and generator, generating electricty
3. Biofuel, obtained from living organisms, could be burnt instead
4. Uranium can undergo fission to heat water

1. Wind
   1. Turns turbines directly
2. Water
   1. Hydroelectric
      1. Water flowing downhill to turn turbine
   2. Wave
      1. Uses movement of waves to drive floating turbine
   3. Tidal
      1. Barrage traps water at high tide to fall down, turning the turbine

1. Solar
   1. Solar cells convert sunlight to electrical energy
   2. Solar heating heats water directly
2. Geothermal
   1. Cold water pumped on to hot rocks, generating steam, which turns the turbine

1. Distributes electricity to homes
2. Step-up and step-down transformers used to reduce current in wires, reducing heat loss
3. 230V

1. Base Load- Average demand of electricty
   1. Covered by coal, oil and nuclear
2. Variable demand met by gas power stations, as they have shortest start up time

1. Transverse- Vibration perpendicular to direction
2. Longitudinal- Vibration parallel to direction

1. Amplitude- Height of wave crest
2. Wavelength- Distance from one crest to next
3. Frequency- Waves past a point in 1 second
   1. Hertz- Hz
4. Velocity= Freq. x Wavelength

1. Normal perpendicular to surface
2. Angle of Incidence= Angle of Refraction
3. Image in a mirror is: same size, upright, laterally inverted virtual

1. Change of direction when light enters a new substance
2. More dense- Towards normal
3. Less dense- Away from normal

1. Spreading of waves though a gap
2. Most notable if wavelength same as gap

1. Longitudinal waves
2. Need particles to travel

1. Higher freq.= Higher pitch
2. Higher amplitude= Louder note

Anotações:

• Radio Microwaves Infrared Visible light UV X- Rays Gamma

1. Radio is largest
2. Gamma is smallest
3. Can travel through vacuum

1. White light contains all colours of the spectrum
2. All used for communiaction

1. Radio waves used for communication
2. Microwaves used for satellite TV
3. Mobile phones may not be safe- research needed

1. Doppler Effect- Waves compressed in direction of movement, spread out behind
2. Galaxy- Large collection of stars
3. Red Shift- Light observed from galaxies shifted towards longer wavelength, so are moving away from us
4. Further away, bigger the red shift

1. Release of energy from an initial point
2. Continually been expanding
3. Cosmic Microwave Background Radiation- Electromagnetic radiation created just after Big Bang