SP2a Conservation of energy Flashcards
What is the conservation of energy?
energy cannot be created or destroyed, it can only be transferred from one store to another.
Total energy input = ?
total useful energy output + wasted energy.
What is a system?
any object or group of objects that we wish to consider, e.g. a car.
What is a closed system?
a system which does not allow energy to enter or leave.
State energy stores (7)
kinetic, gravitational potential, elastic potential, chemical potential, thermal, sound, light.
State energy transfers (4)
electrically, mechanically, by radiation, by heating.
Thermal conductivity is?
measure of how easily energy can pass through a material by heating.
Why do thick walls with a low thermal conductivity cause a building to cool slowly?
because the thicker the wall, the slower the rate of energy transfer.
What does dissipated mean?
when energy is transferred to the thermal store of the surrounding and it spreads out.
All mechanical processes are wasteful due to?
friction causing a rise in temperature which heats the surroundings so the energy is dissipated.
Ways of reducing unwanted energy transfers (explain the ways) (2)
thermal insulation - building thick walls, build using materials with a low thermal conductivity.
lubrication - used to reduce friction - ussually oil so they can flow easily between objects and coat them.
