P2 Energy Flashcards
What are the units of energy? (Units and Symbol)
Joules (J)
What is an energy store?
How energy is kept by an object, ready to be used.
State 4 energy stores
Gravitational Potential
Kinetic
Elastic Potential
Thermal (Internal)
Chemical
Magnetic
Electrostatic
Nuclear
Describe how the gravitational potential energy store of an object can increase.
Raise it higher above the ground (higher in gravitational field), or increase the mass of the object.
Describe how the gravitational potential energy store of an object can decrease.
Lower it (closer to centre of gravitational field), or decrease the mass of the object.
Describe how the kinetic energy store of an object can increase.
If it speeds up or increases in mass
Describe how the kinetic energy store of an object can decrease.
If it slows down or decreases in mass
Describe how the elastic potential energy store of an object can increase.
By stretching, compressing or bending (deforming) an elastic object.
Describe how the elastic potential energy store of an object can decrease.
By allowing an elastic object to return to its original size/shape.
Describe how the thermal (internal) energy store of an object can increase.
Increase in temperature or a change of state (solid→liquid→gas)
Describe how the thermal (internal) energy store of an object can decrease.
Decrease in temperature or a change in state (gas→liquid→solid)
Describe how the chemical energy store can change.
Through chemical reactions.
Describe how the magnetic energy store can change.
Changes to the strength of a magnetic field.
Describe how the electrostatic energy store can change.
Changes to the strength of an electric field.
Describe how the nuclear energy store can change.
Changes in the nucleus of atoms.
Give an example of a chemical energy store.
Fuel
Food
Batteries
What is an energy pathway (transfer)?
How energy is moved from one energy store to another?
Name the four energy pathways.
Mechanical (Forces)
Radiation (Waves)
Electrical
Heating
When might an energy transfer take place?
Whenever anything in the universe changes or happens i.e. All the time!
State the principle of conservation of energy.
Energy cannot be created or destroyed, only transferred from one store to another along an energy pathway.
What is work done.
A measure of energy transferred.
State the equation that links work done, force, and distance in words.
Work done = Force x Distance
State the equation that links work done, force, and distance in symbols.
W=Fd
State the units of work done.
Joules (J)
State the units of force.
Newtons (N)
State the units of distance.
Metres (m)
In which direction is energy transferred along the heating pathway?
From hotter objects to colder objects.
What is meant by useful energy?
Energy that is transferred to the store, or along the pathway, that is its intended function.
What is meant by wasted energy?
Energy that is transferred to a store, or along a pathway, that does not support its function. This is usually the thermal store of the surroundings.
What is dissipated energy?
Wasted energy that spreads out into (the thermal store of) the surroundings.
Define Power
Power is energy transferred (work done) per second.
OR
Power is rate of energy transfer
State the equation linking Power, Energy and Time in words.
Power = Energy/Time
State the equation linking Power, Energy and Time in symbols
P=E/t or E=Pt or t=E/P
State the units of time
Seconds (s)
State the units of Power
Watts (W)
What does 1 Watt mean?
An energy transfer of 1 Joule per second.
Approximately what is room temperature (on average)?
20°C
How does temperature difference affect the rate of heat transfer?
Heat will transfer faster when there is a larger temperature difference.
If a cup of boiling water is left out in a room, what is the coldest it will cool to?
Room temperature (approx. 20°C)
If a cup of boiling water is left out in a room, when will it cool down at the fastest rate?
When the temperature of the water is highest (temperature difference to room is greatest).
If a cup of boiling water is left out in a room and cools down, what was the energy transfer?
From the thermal store of the hot water to the thermal store of the surroundings
If a cup of cold water is left out in a room, what is the hottest it will warm to?
Room temperature (approx. 20°C)
If a cup of cold water is left out in a room, when will it warm up at the fastest rate?
When the temperature of the water is lowest (temperature difference to room is greatest).
If a cup of cold water is left out in a room and warms up, what was the energy transfer?
From the thermal store of the surroundings to the thermal store of the water.
When conducting a practical to look at how the number of layers of paper wrapping around a can of hot water affects the rate of cooling, what is the independent variable?
Number of layers of paper
When conducting a practical to look at how the number of layers of paper wrapping around a can of hot water affects the rate of cooling, what is the dependent variable?
Rate of cooling (temperature)
When conducting a practical to look at how the number of layers of paper wrapping around a can of hot water affects the rate of cooling, what are the control variables?
Shape (surface area) of can
Material of can
Volume of water
(Approximately) same starting temperature
Environmental conditions (room temperature)
Substance being cooled (water)
How can the rate of cooling or heating be found from a temperature-time graph?
The gradient of the line.
What sort of materials make good thermal conductors?
Metals (due to delocalised electrons)
Solids - particles are packed close together
What sort of materials make good thermal insulators?
Wood, plastics, ceramics
Gases - particles are spread out
Vacuum (no particles)
Give 3 ways to reduce thermal energy lost from houses
Close windows and doors, Draught excluders, Cavity wall insulation, Loft insulation, Carpets, Curtains, Double glazing
What is the energy transfer that occurs when a fuel is burned to heat water?
Chemical store to thermal store along the heating pathway.
What units of measurement are used to measure energy consumption in homes?
KiloWatt hours (kWh)
Can energy be stored electrically?
Only in small amounts (capacitors).
How can excess energy production be stored?
As gravitational potential energy in pumped (water) storage. As chemical energy in battery banks.
Describe how a thermal power station is used to transfer energy from an energy resource along the electrical pathway.
- Energy resource used to heat water to steam.
- Steam turns turbine
- Turbine turns generator
- Generator transfers energy along electrical pathway.
What is a turbine?
Revolving machine with blades. Can be turned by wind, water or steam.
What is an electrical generator?
Device that converts kinetic energy in to energy that can be transferred along electrical pathway (works like an electric motor in reverse)
Define non-renewable energy resource
An energy resource that is being used at a faster rate than it is replenished.
Define renewable energy resource
An energy resource that is being replenished at a faster rate than it is used.
Define fossil fuel
An energy resource (fuel) that comes from dead organisms from millions of years ago
State the three fossil fuels
Coal, Oil, Natural Gas
Is nuclear a renewable energy resource?
No, it is non-renewable
Is nuclear a fossil fuel?
No
Define finite resource
Something that has a limited supply and will eventually run out.
State one advantage of fossil fuels as an energy resource
Relatively cheap, Infrastructure already exists
State one disadvantage of fossil fuels as an energy resource
Produces greenhouse gases (carbon dioxide), Coal produces sulphur dioxide which can lead to acid rain, Finite resource
State one advantage of nuclear as an energy resource
No greenhouse gas emissions once power station is built, Produces huge amounts of energy in relation to mass of fuel
State one disadvantage of nuclear as an energy resource
Large amount of concrete used in power station construction that releases greenhouse gases (CO2), Environmental impacts of nuclear waste, Potential for large scale disaster (very rare), Finite resource
What is meant by tidal energy?
Electricity that is produced by movement of water due to tidal flow.
What is meant by wave energy?
Electricity that is produced by movement of water due to waves.
What is meant by hydroelectricity?
Electricity that is produced by movement of water due to it flowing downhill. Often dams are used to allow build up of larger quantities of water.
What is meant by solar power?
Energy from absorbing radiation from the sun.
What is meant by biomass energy?
Electricity that is produced from burning organic matter.
What is meant by biogas energy?
Electricity that is produced from burning gas produced from organic matter.
What is meant by wind power?
Electricity that is produced by movement of air particles due to weather.
Give two reasons why the UK is still reliant on fossil fuels?
Non-renewable energy is often cheaper per kWh.
Renewables and nuclear not currently able to meet energy demands.
Renewable sources are not always reliable and may take time to ramp up to demand.
