energy Flashcards
What are the stores of energy?
chemical, thermal, kinetic, gravitational potential, elastic, potential, nuclear, sound, light, electric and magnetic
Units for energy
Joules
Describe conservation of energy
Energy can be transferred from one form to another but can’t be created or
destroyed
Energy input =
Useful energy + wasted energy
Define wasted energy
Energy that is not in a useful format that is dissipating
Work done =
Force applied x distance move
Efficiency =
Useful energy transferred / total energy supplied by the device
Power =
Energy transferred to appliance / time taken for the energy to be transferred
What is the power of 1 watt equal to?
An energy transfer of 1 Joule per second
What happens if the motor is powerful?
It moves a particular load faster
Potential energy =
mass x gravitational field strength x
change of height
Kinetic energy =
½ mass x speed2
How efficient are energy transfers?
Not 100% efficient, all efficiencies exist between 0-100%
Describe useful energy
Energy transferred into the form of energy that is wanted
Describe wasted energy
Energy transferred into a form of energy that is not useful (often thermal store or sound store)
How do you make an appliance more energy efficient? Give examples
You must reduce the amount of wasted
energy. Eg lubrication, tightening loose or moving particles, reducing
electrical resistance
Describe metals energy transfer
Best conductors with a high energy transfer
Describe non-metals energy transfer
Insulators with a low energy transfer
Describe convection
The movement of heat in fluids. The particles in the fluid become less
dense when hot, rise and float. When cold the particles become denser and sink.
How do hot objects radiate heat
In the form of waves. There is no need for particles
Why are houses are insulated?
To prevent energy loss and save energy resources and money.
Describe double glazing’s function
Preventing heat loss because they have a trapped layer of gas so both
conduction and convection cycles are disrupted.
Why are insulating panels made of foam and coated with foil
It reduces radiation, conduction and convection.
All objects ______ and _______ radiation. The ________ the more it gives out.
All objects emit and absorb radiation, the hotter the more it gives out.
