P1 Energy
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What are examples of energy stores
Chemical,kinetic,gravitational potential, elastic potential, thermal
How can you show energy transfers
Using flow diagrams Showing how energy stores are transferred
What is a closed system
A system where no energy can be transferred from any energy stores
What is the principle of conservation of energy
Energy cannot be created or destroyed
What equation links energy transferred and work done
Energy transferred = Work done
What is hooke’s law
F=ke where k is the spring constant
What is useful and wasted energy
Useful energy is energy transferred to where it is wanted in the way that is wanted Wasted energy is the energy that is not usefully transferred
What is the energy supplied called
The input energy
Because energy cannot be created or destroyed the input energy =
Useful output energy + energy wasted
Why do devices waste energy
Friction between the moving parts cause heating (Fixed with lubrication) Resistance in wires cause heat(use wires with little resistance) Air resistance causes opposing forces(use more streamline shapes) Sound created by machinery(cut out noisy parts)
The more powerful an appliance is, the faster the rate at which it transfers ______
Energy
What is 1 watt equal to
1 joule of energy in seconds
Give the definition and an example of a chemical energy store.
The type of energy transferred in a chemical reaction. E.g. Fuels, Foods, Chemicals in batteries
Give the definition and an example of a kinetic energy store.
The type of energy in an object that is moving. E.g. ball rolling down a hill
Give the definition and an example of a thermal energy store.
The energy a substance has because of its temperature. E.g. hot drink
Give the definition and an example of a gravitational potential energy store (GPE).
The energy an object has based on its position. E.g. a ball above ground
Give the definition and an example of an elastic potential energy store.
The energy stored in an object when it is squashed or stretched. E.g. rubber band, compressed spring
What does a machine do in terms of energy?
It transfers energy for a purpose
What happens to wasted energy in a machine?
It is dissipated to the surroundings
What happens to energy as it is spread out?
It becomes less useful the more it spreads