Physics P1

Physics P1

1. Energy Transfer by Heating

   • infrared Radiationi
     • Form of electromagnetic wave
     • Emitted by all objects
     • Detected as heat
   • Surfaces and Radiation
     • Black matt surfaces both emit and absorb IR the best
     • White shiny surfaces are the worst absorbers and emitters of IR
   • States of Matter
     • Solid
       • Particles in uniform format, vibrating in a fixed position
     • Liquid
       • Particles move about at random
       • Still in contact with each other
     • Gas
       • Move about randomly with high kinetic energy
       • Particles much further apart and not in contact
   • Conduction
     • Conduction in Metals
       • Metals are best conductors
       • Delocalised free electrons transfer vibration down the material by colluding with the other particles
     • Insulator- Poor conductor
     • Particles near the heat source gain kinetic energy and vibrate more. This movement is passed on to neighbouring particles
   • Convection
     • Occurs in fluids
     • Heating causes the fluid to become less dense, therefore it rises and is replaced by the cooler particles
       • Causes convection currrent
   • Evaporation and Condesation
     • Evaporation
       • When a liquid turns into a gas
       • Particles with the highest kinetic energy escape, taking energy with it, causing cooling
       • Rate increased by
         • Increasing surface area of liquid
         • increasing temperature of liquid
         • Draught across surface
     • Condensation
       • When gas turns to liquid
       • Rate increased by
         • Increasing surface area
         • Reducing surface temperature
   • Energy Transfer by Design
     • Heat goes from hot to cold
       • Greater the temperature difference between object and surroundings, wuicker energy is transfered
     • Maximise transfer
       • Use good conductors
       • Matt black
       • Air flow
     • Minimise transfer
       • Use of insulators
       • White and shiny
       • Trapped air
   • Specific Heat Capacity
     • Energy required to heat 1kg of a substance by 1 degree
       • Greater mass more energy needed
     • E=mass x SHC x temp. change
     • J/kg(o)C
   • Heating and Insulating Buildings

2. Using Energy

   • Forms of Energy
     • Light Sound Kinetic Thermal Nuclear Gravitational Potential Elastic Potential Magnetic Electrical Chemical
     • Transferred from one type to another
   • Conservation of Energy
     • Energy cannot be created or destroyed
     • Total energy always the same
   • Useful Energy
     • Useful Energy- Transferred where and in the form we want
     • Wasted Energy- Not useful energy
     • All eventually transferred to surroundings, making it harder to use
   • Energy and Efficiency
     • Efficiency= (Useful energy/ Total energy supplied) x100
     • Can't be more than 100% efficient
     • Represented in Sankey diagram

3. Electrical Energy

   • Electrical Appliances
     • Transfers electricity into any useful form
     • Should waste as little energy as possible
   • Electrical Power
     • Power- Rate it transfers energy
       • Watt
         • 1kW=1000W
     • Power= Energy/ Time
   • Using Electrical Energy
     • Kilowatt-hour- Energy transferred to kW appliance in an hour
     • Energy= Power x Time
       • kw=kW x h
     • Total cost= Number of kWh x Cost per kWh
   • Cost Effectiveness Matters
     • Best value for money
     • Payback Time- Time for appliance to save same as it cost
       • Payback Time= Cost/ Saving per year

4. Generating Electricity

   • Fuel for Electricity
     • Fossil fuel burnt to turn wter to steam
     • Steam turn turbine and generator, generating electricty
     • Biofuel, obtained from living organisms, could be burnt instead
     • Uranium can undergo fission to heat water
   • Energy from Wind and Water
     • Wind
       • Turns turbines directly
     • Water
       • Hydroelectric
         • Water flowing downhill to turn turbine
       • Wave
         • Uses movement of waves to drive floating turbine
       • Tidal
         • Barrage traps water at high tide to fall down, turning the turbine
   • Power from the Sun and the Earth
     • Solar
       • Solar cells convert sunlight to electrical energy
       • Solar heating heats water directly
     • Geothermal
       • Cold water pumped on to hot rocks, generating steam, which turns the turbine
   • Energy and the Environment
   • The National Grid
     • Distributes electricity to homes
     • Step-up and step-down transformers used to reduce current in wires, reducing heat loss
     • 230V
   • Big Energy Issues
     • Base Load- Average demand of electricty
       • Covered by coal, oil and nuclear
     • Variable demand met by gas power stations, as they have shortest start up time

5. Waves

   • Nature of Waves
     • Transverse- Vibration perpendicular to direction
     • Longitudinal- Vibration parallel to direction
   • Measuring Waves
     • Amplitude- Height of wave crest
     • Wavelength- Distance from one crest to next
     • Frequency- Waves past a point in 1 second
       • Hertz- Hz
     • Velocity= Freq. x Wavelength
   • Reflection
     • Normal perpendicular to surface
     • Angle of Incidence= Angle of Refraction
     • Image in a mirror is: same size, upright, laterally inverted virtual
   • Refraction
     • Change of direction when light enters a new substance
     • More dense- Towards normal
     • Less dense- Away from normal
   • Diffraction
     • Spreading of waves though a gap
     • Most notable if wavelength same as gap
   • Sound
     • Longitudinal waves
     • Need particles to travel
   • Musical Sound
     • Higher freq.= Higher pitch
     • Higher amplitude= Louder note

6. Electromagnetic Waves

   • Electromagnetic Spectrum
     • Radio Microwaves Infrared Visible light UV X- Rays Gamma
     • Radio is largest
     • Gamma is smallest
     • Can travel through vacuum
   • Light, Infrared, Microwaves and Radio Waves
     • White light contains all colours of the spectrum
     • All used for communiaction
   • Communication
     • Radio waves used for communication
     • Microwaves used for satellite TV
     • Mobile phones may not be safe- research needed
   • Expanding Universe
     • Doppler Effect- Waves compressed in direction of movement, spread out behind
     • Galaxy- Large collection of stars
     • Red Shift- Light observed from galaxies shifted towards longer wavelength, so are moving away from us
     • Further away, bigger the red shift
   • Big Bang
     • Release of energy from an initial point
     • Continually been expanding
     • Cosmic Microwave Background Radiation- Electromagnetic radiation created just after Big Bang