P1 OCR

P1 OCR

1. Heat and Temperature

   • Energy is transferred from a hotter to a colder body.
   • Temperature is a measure of HOTNESS on an arbitrary scale, measured in DEGREES CENTIGRADE.
   • Energy is a measure of ENERGY TRANSFER on an absolute scale, measures in JOULES.
   • Energy is transferred when a substance changes temperature.
     • The amount of energy transferred depends on the mass and the specific latent heat.
       • Energy transferred = mass x specific latent heat
   • The amount of energy transferred depends on the mass, temperature change and specific heat capacity.
     • energy transferred = mass x specific heat capacity x temperature change

2. Energy Transfer

   • Air is a good insulator and reduces energy transfer by conduction
     • Conduction in a solid is by the transfer of kinetic energy
   • Trapped air reduces energy transfer by convection
     • Convection currents are caused by changes in density
   • Energy saving in the home can be achieved by:
     • Double glazing
     • Cavity wall insulation
     • Draught excluders
     • Reflecting foil
     • Loft insulation
     • Curtains
     • Careful design
   • Shiny surfaces reflect infrared radiation to reduce energy transfer
   • Energy transformations can be represented by diagrams
   • Efficiency = useful energy output (x100%) / total energy input

3. Waves Transfer Energy

   • Warm and hot objects emit infrared radiation
   • Infrared radiation is used for cooking
   • Microwaves can be used for cooking and communication when transmitter and receiver are in line of sight
   • Laser light is single colour and in phase
   • Laser light, visible light and infrared are all used to send signals along optical fibres by total internal reflection
   • Digital and analogue signals are used for communication
     • Morse is a digital code
     • Digital signals allow many signals to be transmitted at the same time
     • Digital signals are clearer
   • Radio waves are used for communication
     • Longer wavelengths diffract around obsticles
   • Radio waves, microwaves, infrared, visible light and ultraviolet are some of the waves in the electromagnetic spectrum
     • The energy of the wave increases as the wavelength decreases
     • All electromagnetic waves can be reflected, refracted and diffracted
     • All waves have amplitude, frequency and wavelength: wave speed = frequency x wavelength

4. The Stable Earth

   • Earthquakes can travel through the earth
   • Different waves help us to find out about the inside of the earth
   • Exposure to ultraviolet radiation causes sun burn and skin cancer
   • Sunscreen and sunblock reduces damage caused by ultraviolet radiation
   • CFCs are causing the ozone layer to become thinner