List the 8 energy stores.
Thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic and nuclear.
How is energy transferred?
Mechanically (force doing work), electrically (work done by moving charges), heating and radiation (light or sound).
What is a system?
A single object or group of objects. When a system changes, energy is transferred.
What is a closed system?
A system wher no matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero.
How do you calculate kinetic energy?
Kinetic energy (J) = 1/2 x mass (kg) x velocity² (m/s)² or E=1/2mv².
How do you calculate gravitational potential energy?
GPE (J) = mass (kg) x gravitational field strength (N/kg) x height (m) or E=mgh.
How are gpe and kinetic energy connected?
When there is no air resistance, energy lost from gpe store = energy gained in the kinetic store.
How do you calculate elasic potential energy?
Elastic potential energy (J) = 1/2 x spring constant (n/m) x extension² (m) or E=1/2ke².
What is the limit of proportionality?
When the extension is no longer proportional to the force.
What is specific heat capacity?
The amount of energy needed to raise the temperature of 1 kg of a substance by 1°C.
What equation links energy transferred to specific heat capacity?
Change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg°C) x temperature change (°C) or ΔE=mcΔθ.
How would you investigate the specific heat capacity of different solid materials?
- You will need a block of the material with two holes in it for the heater and thermometer.
- 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.
- Measure the initial temperature of the block and set the potential difference of the power supply to 10V. Turn on the the power supply and start a stopwatch.
- When you turn on the power, the current in the circuit does work on the heater, transferring energy electrically from the power supply to the heater’s thermal energy store. This energy is then transferred to the material’s thermal energy store by heating, causing the materials temperature to increase.
- As the block heats up, take readings of the temperature and current every minute for 10 minutes.
- Turn off the power supply once you have collected enough readings. Calculate power supplied to the heater using P=VI. You can then calculate how much energy is transferred to the heater (E=Pt).
- You can then plot a graph and calculate specific heat capacity.
- Then repeat this experiment with different materials to compare.
What is the conservation of energy principle?
Energy can be transferred usefully, stored or dissipated, but can never be created or destroyed.
How can you calculate power?
P=E/t or P=W/t.
What is conduction?
The process where vibrating particles transfer energy to neighbouring particles.
What is thermal conductivity?
A measure of how quickly energy is transferred through a material.
What is convection?
Where energetic particles move away from hotter to cooler regions.
How does convection work?
When you heat a region of liquid or gas, the particles move faster and the space between the individual particles increases. This causes the density of the region being heated to decrease. The warmer less dense region will rise above the denser, cooler regions. A convection current is created if there is a constant heat source.
How does a radiator heat a room (convection currents)?
- Energy transferred from the radiator to the particles nearby.
- The air by the radiator becomes warmer and less dense.
- The warm air rises and is replaced by cooler air. The cooler air is then heated by the radiator.
- Previously heated air transfers energy to the surroundings, cools, becomes denser and sinks.
- The cycle repeats.
How can you reduce wasted energy from friction?
Lubricants like oil.
How can you reduce energy loss through heating?
Thick walls that are made from a material with a low thermal conductivity.
Use thermal insulation:
- cavity walls (air gap in the middle filled with foam)
- lost insulation
- double glazing
- draught excluders.
How can you calculate efficiency?
Efficiency = useful output energy transfer/ total input energy transfer.
or efficiency = useful power output/ total power input.
How can you improve the efficiency of energy transfers?
Insulating objects, lubricating them, making them more streamlined.
What are the three main fossil fuels?
- Coal.
- Oil.
- Natural Gas.
