Energy Stores And Transfers Flashcards
(32 cards)
What are the seven main energy stores?
Magnetic, thermal, chemical, kinetic , electrostatic, elastic potential and gravitational potential
What are the four main transfers of energy?
Mechanical work, electrical work, heating and radiation
Define work done
The amount of energy it takes to do a task. Measured in joules (J).
For example, the work done in raising a mass through 10 m would be equal to the gain in potential energy of the mass.
What is a system?
An object or group of objects
What do transfer diagrams show, what do the boxes show?
Transfer diagrams show the stores of energy and the transfers between them.
The boxes in a transfer diagram show the energy stores and the arrows show the energy transfers.
What are Sankey diagrams?
Sankey diagrams show how much of the total energy of a system is transferred into stores
Sankey diagrams start off as one arrow that splits into two or more points. This shows how much of the total energy in a system is transferred into different stores.
What is the conservation of energy give an example.
Energy can be transferred usefully, stored or dissipated, but it cannot be created or destroyed. The total energy before a system changes is equal to the total energy afterwards.
An example of conserving energy is when a ball rolls downhill. The amount of gravitational potential energy lost equals the gain in kinetic energy of the ball, plus the heat energy dissipated in the ball and the ground.
What does dissipated mean
The spreading out and transfer of energy stores into less useful forms, such as thermal energy causing the surroundings to heat up.
Dissipated energy is often referred to as ‘wasted’ energy, since it is not transferred to a useful output.
Why do we get energy dissipation? How is it usually lost. Give an example of it.
No system is perfect - whenever energy is transferred, some of that energy is dissipated. Any energy that is not transferred to useful energy stores is said to be wasted because it is lost to the surroundings - it is dissipated.
e.g. Electrical cables getting hot is an example of this. Energy is lost or dissipated as the hot wire heats the surrounding air.
What is elastic potential energy? Give examples.
Energy stored in squashed, stretched or twisted materials.
e.g. Drawn catapults, compressed springs, inflated balloons.
What is thermal energy? Give examples.
The total kinetic energy and potential energy of the particles in an object.
e.g. Human bodies, hot coffees, stoves or hobs. Ice particles vibrate slower, but still have energy.
What is a magnetic energy store? Give examples.
The energy stored when repelling poles have been pushed closer together or when attracting poles have been pulled further apart.
e.g. Fridge magnets, compasses, maglev trains which use magnetic levitation.
What is kinetic energy store? Give examples.
The energy stored in moving objects.
Stationary objects have no kinetic energy.
e.g. a moving car, tennis ball
What is Gravitational potential energy? Give examples.
Gravitational potential energy is the energy stored in an object due to its position above the earths surface.
What is specific heat capacity?
The Specific Heat Capacity of a substance is the amount of energy required to raise the temperature of 1 kg of the substance by 1°C.
Describe the method for the specific heat capacity required practical.
1) Place a beaker on a balance and press 0.
2) Add oil to the beaker and measure the mass of oil.
3) Place a thermometer and immersion heater into the oil
4) Connect a joulemeter to the immersion heater.
5) Time for thirty minutes
6) Tead the final temperature of oil.
Sources of inaccuracy in the specific heat capacity required practical.
- Thermal energy passing out of the beaker into the air
- Not all thermal energy passing into the oil.
- Use an insulator with a low thermal conductivity.
- Ensure that immersion heater is fully submerged.
Method for thermal insulators squired practical.
1) First place a small beaker inside a larger beaker
2) Use kettle to boil water
3) Transfer 80cm cubed of hot water into the small beaker
4) Use a piece of cardboard as a lid for the large beaker.
5) Place a thermometer through the whole in the cardboard.
6) Record starting temperature and set a stopwatch.
7) Record the temperature every 3 minutes for 15minutes.
8) Repeat with the same volume of water but with an insulating material e.g. bubble wrap.
Test a range of materials.
Use the same mass of material.
Can do the same with thickeners, change the amount of layers.
Advantages of fossil fuels.
- Reliable ; provide energy when we need it.
- Release a great deal of energy
- Versatile
What is the law of the conservation of energy ?
Energy can be transfered usefully, stored or dissipated but it cannot be created or destroyed.
How can we reduce unwanted energy transfers?
By reducing friction
e.g. lubricant
What is power?
The rate at which energy is transferred/work done.
What is efficiency?
The fraction of energy we put into an appliance is transferred to useful forms of energy.
What does thermal conductivity mean?
The highest the thermal conductivity of a material, the higher the rate of energy transfer by conduction across that material
