AQA Physics P1
P1
AQA
–
Revision
Notes
1. Heat Transfer
• Thermal radiation = infra-red radiation (beyond red part of visible spectrum)
• Surface of sun is 5500 degrees.
• Greenhouse effect is the idea that the earth is a greenhouse, and the atmosphere is glass that stops substances exiting or entering.
• DARK, MATT SURFACES emit more radiation than shiny, light ones, and absorb radiation better.
• Conduction: free electrons are given energy where heated and diffuse – this energy is passed on as electrons collide. o A conductor can pass on this energy much quicker.
• Shiny, light surfaces reflect radiation the best.
• Convection occurs with only liquids or gases.
• Hot, light air rises, whilst cold, dense air sinks. This causes convection current in gases and liquids.
• This occurs because fluids expand when heated making them lighter.
• Vacuum flask: o Vacuum cuts out heat transfer by conduction and convection. o Glass is poor conductor so little heat conducted here. o Glass surfaces are silvery to reduce radiation from outer wall.
• Homes: o Double glazed window with vacuum reduces conduction. o Cavity wall insulates reducing heat loss. o Loft insulation reduces heat loss through roof.
2. Using Energy
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•
•
•
•
•
•
•
Chemical energy – stored in fuel (food aswell)
Kinetic energy – movement
Gravitational potential energy – due to position
Elastic energy – stored in springy object
Electrical energy – transferred by electric current
Thermal energy – due to temperature.
Energy is ALWAYS transformed, never created or destroyed.
This is the CONSERVATION OF ENERGY.
•
•
•
•
•
Useful energy transferred to where it is wanted.
Wasted energy is not used.
Wasted energy spreads out to the surroundings, e.g. as heat
Weight is measured in newtons (N).
Efficiency = useful energy transferred
Total energy supplied
• We can show energy transferral as a Sankey Diagram.
3. Electrical Energy
Power (W) = rate of transfer of energy
1. Heat Transfer
• Thermal radiation = infra-red radiation (beyond red part of visible spectrum)
• Surface of sun is 5500 degrees.
• Greenhouse effect is the idea that the earth is a greenhouse, and the atmosphere is glass that stops substances exiting or entering.
• DARK, MATT SURFACES emit more radiation than shiny, light ones, and absorb radiation better.
• Conduction: free electrons are given energy where heated and diffuse – this energy is passed on as electrons collide. o A conductor can pass on this energy much quicker.
• Shiny, light surfaces reflect radiation the best.
• Convection occurs with only liquids or gases.
• Hot, light air rises, whilst cold, dense air sinks. This causes convection current in gases and liquids.
• This occurs because fluids expand when heated making them lighter.
• Vacuum flask: o Vacuum cuts out heat transfer by conduction and convection. o Glass is poor conductor so little heat conducted here. o Glass surfaces are silvery to reduce radiation from outer wall.
• Homes: o Double glazed window with vacuum reduces conduction. o Cavity wall insulates reducing heat loss. o Loft insulation reduces heat loss through roof.
2. Using Energy
•
•
•
•
•
•
•
•
Chemical energy – stored in fuel (food aswell)
Kinetic energy – movement
Gravitational potential energy – due to position
Elastic energy – stored in springy object
Electrical energy – transferred by electric current
Thermal energy – due to temperature.
Energy is ALWAYS transformed, never created or destroyed.
This is the CONSERVATION OF ENERGY.
•
•
•
•
•
Useful energy transferred to where it is wanted.
Wasted energy is not used.
Wasted energy spreads out to the surroundings, e.g. as heat
Weight is measured in newtons (N).
Efficiency = useful energy transferred
Total energy supplied
• We can show energy transferral as a Sankey Diagram.
3. Electrical Energy
Power (W) = rate of transfer of energy