Energy Flashcards
What is a system
An object or group of objects
What is the equation for kinetic energy
0.5 x mass x speed(squared)
What is the equation for elastic potential energy
0.5 x spring constant x extension (squared)
What is the equation for gravitational potential energy
Mass x gravitational field strength x height
What are examples of energy stores
Kinetic energy store
Gravitational potential store
Chemical store
Elastic potential store
Nuclear store
Internal store
What is specific heat capacity
The amount of energy needed to raise the temperature of 1 kilogram of a substance by 1 degree Celsius
What happens if you increase an objects temperature
Increases the energy in the kinetic store of the bodies particles meaning that the energy in the objects internal store also increase
What is the law of conservation
Energy cannot be created or destroyed. Instead it can only be transferred
What happens with mechanical work
Energy transferred from 1 object to another via a force is an example of mechanical work
What happens with electrical work
An electrical current transfers energy from one object to another like a battery powering a torch
What are the energy changes when a ball is thrown upwards
Upwards-KE is converted into GPE
peak-maximum GPE zero KE
Downwards- GPE converted to KE
What are the energy transfers for a bungee jumper
When falling-GPE converted to KE
As cord tightens KE converted to EPE
lowest point- jumpers initial GPE equals the EPE stored in the cord
Why does a bungee jumper slow down once the chord begins to stretch
Kinetic energy decreases since it is converted to elastic potential energy
Since kinetic energy is proportional to velocity (squared) as kinetic energy decreases so does the velocity
What happens if more work is done
Push with the same force for a longer distance or push with a larger force for the same distance
What is the equation for work done
Work done = force x distance
What is the definition of power
The rate at which energy is transferred
What are the two equations for power
Power=energy transferred over time
Power=work done over time
Two mothers lift the same mass through the same height. Motor A does this in half the time of Motor B. Which dissipates the most power?
Motor A. The energy transferred is the same but the time taken is less
What are examples of chemical energy stores
Food
Fuel
Batteries
What is waste energy
The energy that is not used by the device for its desired purpose
What is an example of wasted energy
Friction- in almost encrypted energy transfer friction creates heat energy and this energy is wasted
Describe the energy changes that occur in a filament light bulb
Electrical energy is transferred into light and heat energy
Light in a useful energy form however heat is waste energy
How can you calculate efficiency of energy transfers
Useful output energy transfer/Total input energy transfer
Useful power output/total power output
How can the efficiency of a system be increased
Reducing waste output
Recycling waste output
What is a consequence for energy transfer of a material with a high thermal conductivity
Rate of energy transfer through the material is higher than for a material with a lower thermal conductivity
How can you reduce unwanted energy
Lubrication-can reduce the friction between surfaces of objects causing some energy to be dissipated
Thermal insulation-as heat will be lost through roof windows walls and floors
How can the efficiency of a radiator be improved
Installing metal foil sheets behind the radiator to reflect the Heat back into the room rather than it being absorbed into the walls
How can the efficiency of boiling water in a pan be improved
By placing a lid on the pan to reduce the heat loss from the top
What is a renewable energy resource
An Energy source which can be replenished as it’s being used up
What are the example of renewable resources
Wind
Geothermal
Hydroelectric
Tidal
Solar
What is an example of a non renewable energy resource
Fossil fuels like coal oil or gas
What are the disadvantages to using renewable energy
Often determined by external factors like wind speed so supply is uncertain
Generating power through other means is often more efficient and economically beneficial
What are the environmental impacts of burning fossil fuels
Carbon dioxide contributed to the greenhouse effect and caused global warming
Supper dioxide leads to acid rain which can damage buildings and crops
What are the advantages of fossil fuels as an energy resource
Reliable- not dependant on external factors
Can produce large amounts of energy for a given quantity
Still relatively abundant so cost effectivr
Used for more large scale energy supplies due to large energy output per kg of fuel
What are the advantages of solar panels
Don’t harm the environment
Renewable
Can be used in remote areas
How has the uk increased renewable energy
Government policy-governments are introducing targets for renewable energy
Power plants- energy providers are building power plants that use renewable resources
Vehicles-vehicle makers are creating electric use
Renewable energy has become more important due to the finite lifetime of fossil fuels
What are the limits of renewable energy
Cost-expensive to build power plants
Reliability-less reliable than fossil fuels
Politics-may not be keen on renewable
What is the method for determining specific heat capacity
1)set up your equipment ensuring to wrap insulation around the base and sides of the block.
2) if the thermometer has an air gap surrounding it when placed into the second hole, drop water into the hole using a pippette to increase thermal contact
Method for specific heat capacity (2)
3) if the power of the heater is unknown switch on the power supply and measure the current and potential
Calculate the power using Power=current x potential difference
4) keep the power supply on and start the timer. Measure the temperature of the block every 10 minutes
Specific heat capacity method (3)
5) plot a graph of temperature against work done by the heater. Calculate the gradient of the line
6) specific heat capacity is the gradient divided by the mass of the block. Since the mass is 1 kg the inverse of the gradient is the specific heat capacity of the block
What are the main energy uses
Transport
Electricity generation
Heating
What are the patterns and trends of energy use
During industrial revolution fossil fuels became an important source of energy as it was easy to mine and provided lots of energy
Only recently had renewable energy become more suitable- technology has ad to develop a lot to harness such energy sources efficiently
Easier to use energy resources due to increasing pressure to cope with the publics power demands but harder to solve environmental issue due to political social ethical and economic considerations