Energy Flashcards
Describe:
Law of Conservation of Energy
Energy can be transferred usefully, dissipated or stored but never created or destroyed
List:
Energy Stores
Thermal
Kinetic
Gravitational Potential
Elastic Potential
Chemical
Magnetic
Electrostatic
Nuclear
List:
Energy Transfers
Mechanically
Heating
Radiation
Define:
System
An object or group of objects
Define:
Closed System
A system where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero.
Define:
Work Done
Energy Transferred
Can be when current flows or when a force acts on an object
Equation:
Kinetic Energy
Ek = ½mv²
Equation:
Gravitational Potential Energy
Ep = mgh
Equation:
Elastic Potential Energy
Ee = ½ke²
Define:
Specific Heat Capacity
The energy required to heat 1kg of a material by 1℃
Equation:
Change in Thermal Energy
∆E = mc∆⊖
Mass × Specific Heat Capacity × Change in temperature
Required Practical:
Specific Heat Capacities
1) Get a block of the material with two holes in it
2) Measure the mass of the block, then wrap it in an insulating layer to reduce the energy transferred from the block to the surroundings. Insert the thermometer and heater into the holes
3) Measure the initial temperature of the block and set the potential difference of the power supply to 10V. Turn on the power supply and start a stopwatch
4) As the block heats up, take readings of the temperature and the current every minute for 10 minutes. You should find that the current doesn’t change as the block heats up
5) When you’ve collected enough readings, turn off the power supply. Using your measurement of the current, and the potential difference of the power supply, you can calculated the power supplied to the heater, using P = IV. You can use this to calculate how much energy has been transferred to the heater at the time of each temperature reading using the formula E = Pt
6) If you assume all energy supplied to the heater has been transferred to the block, you can plot a graph of energy transferred to the thermal energy store of the block against the temperature.
7) Find the gradient of the straight part of the graph using Change in Temperature / Change in Energy. So the specific heat capacity of the block is 1 / (Gradient x Mass)
8) Repeat the experiment with different materials to see how their specific heat capacities compare
Define:
Power
The rate of energy transfer or the rate of doing work
(Measured in Watts)
Equation:
Power
P = E/t
P= W/t
Define:
Conduction
The process where vibrating particles transfer energy to neighbouring particles
Define:
Convection
Where energetic particles move away from hotter to cooler regions
Describe:
Lubrication
Reduces frictional forces
Describe:
Insulation
Reduces the rate of energy transfer by heating
Required Practical:
Effectiveness of Thermal Insulators
1) Boil water in a kettle. Pour some of the water into a sealable container to a safe level. Measure the mass of the water in the container
2) Use a thermometer to measure the initial temperature of the water
3) Seal the container and leave it for five minutes. Measure this time using a stopwatch
4) Remove the lid and measure the final temperature of the water
5) Pour away the water and allow the container to cool to room temperature
6) Repeat this experiment, but wrap the container in a different material once it has been sealed. Make sure you use the same mass of water at the same initial temperature each time
7) The lower the temperature difference the better that the material is as a thermal insulator. You should find materials like bubble wrap or cotton wool are good insulators
8) You could also investigate how the thickness of the material affects how good a thermal insulator it is. You should find that the thicker the insulating layer, the smaller the temperature change of the water, and so the less energy is transferred. This means that thicker layers make better thermal insulators
Equation:
Efficiency
Efficiency = Useful output / Total input
Define:
Non-renewable Energy Resources
Fossil fuels and nuclear fuels that will run out one day.
They are used up faster than new ones are produced
List:
Non-renewable Energy Resources
Coal
Oil
Natural Gas
Uranium
Plutonium
Define:
Renewable Energy Resources
Will never run out
List:
Renewable Energy Resources
Solar
Wind
Water waves
Hydro-electricity
Bio-fuel
Tidal
Geothermal
