P1.2 Using Energy Flashcards
What are the nine types of energy?
Kinetic Thermal Chemical Nuclear Gravitational potential Elastic potential Sound Electrical Light
What is the energy transfer diagram of pinging an elastic band?
Elastic potential -> kinetic + sound + thermal + gravitational potential
What’s the energy transfer diagram of an explosion?
Nuclear -> light + thermal + sound + chemical
Why is thermal energy produced a lot in energy transfer diagrams?
Because of friction
What are the energy transfer diagrams for someone bungee jumping?
As the person falls: Gravitational potential -> kinetic As jumper get pinged back: Gravitational potential + kinetic -> elastic When person rises to the top: Elastic -> GP + kinetic Then Gravitational potential -> thermal
What’s useful energy?
Energy transferred to where it’s wanted
What’s wasted energy?
Energy that isn’t usefully transferred
What happens to wasted energy?
It spreads out to the surroundings
In an electric heater what’s the useful energy and the wasted energy?
Useful : thermal
Wasted: sound
In a TV what’s the useful energy and the wasted energy?
Useful: sound + light
Wasted: thermal
What’s the energy transfer diagram for a pendulum?
GP -> kinetic -> GP
What’s the conservation of energy?
Energy can’t be created or destroyed, only transferred
What’s efficiency?
A measure of how good a device is at changing energy from one to another.
The more efficient the device is, the ______ energy is wasted.
Less
How do you calculate efficiency?
Useful energy out / total energy in
What’s the unit for efficiency? How can you tell if your right?
Doesn’t have units
It’s a number between 0 and 1 or a percentage.
In a radio: 300J = electrical energy 96J = sound energy A)How much energy is wasted? B)What energy is wasted? C)What's the efficiency?
A) 300-96 = 204J
B) heat energy
C) 96/300 = 0.32 or 32%
What key things do you have to remember for a sankey diagram?
Input energy is on the left
Useful energy goes out to the right
Wasted energy goes down
Everything has to be to scale eg. 10J = 1 square
What’s the approximate efficiency of a filament bulb?
5%
