Energy Flashcards
What energy changes occur when:
an object projected upwards
a moving object hitting an obstacle
an object accelerated by a constant force
a vehicle slowing down
bringing water to a boil in an electric kettle.
- KE to GPE
- CE to KE to dissipated (TE - sound) to TE of obstacle, object
- CE to KE
- KE to dissipated (TE - sound) to TE brakes
- TE kettle heating component to TE water
RP1. Describe a practical you could use to determine SHC values.
- Set up a power supply, ammeter and aluminium block with an immersion heater and thermometer in, in series. Connect the voltmeter in parallel with the heater.
- Take the initial temperature of the block with the thermometer.
- Set the power supply to maximum output and start the stopwatch.
- While the power supply supplies energy to the heater, the heater will heat up the block. Every minute, record the temperature of the aluminium block using the thermometer, the voltage from the voltmeter and current from the ammeter. Record all these values in a table up to 10 minutes.
- We can rearrange the equations E=QV and Q=It to get E=IVt. For each time period, find the product of your values of current and voltage and time to calculate the energy transferred to the block at this point.
- Use the equation for SHC, Change in energy= massSHCtemperature change, to calculate thee SHC. Use the mass of the block, the calculated energy change value and the temperature change over the selected time period to calculate the SHC.
- Plot a graph of temperature on the y axis and energy on the x axis. It will be linear and 1/gradient=SHC.
Systematic error: zero error of voltmeter and ammeter.
Random error: dissipated energy, insulate block; misreading equipment, joulemeter; and parallax error, eye level to thermometer.
Hazards: hot water, hot equipment,
Risks: burns, spitting, scalding
Prevention: allow equipment to cool, eye protection
Give an example that illustrates the definition of power.
Comparing two electric motors that both lift the same weight through the same height but one does it faster than the other.
How does lubrication work, give examples.
Reduces frictional forces which cause surfaces to heat up and energy dissipates. Examples include rollers, ball bearings and oil.
How does thermal insulation work?
Barrier between areas. Reduces conduction as insulating materials are poor thermal conductors and there is another barrier for thermal conduction to occur across. Can reduce radiation.
How do you reduce unwanted energy transfers in a house?
Carpets, draught excluders, curtains, foil behind radiators, double glazing, cavity wall and loft insulation, layers on walls of materials with low thermal conductivity and thicker walls.
RP2. Describe an investigation into the effectiveness of different materials as thermal insulators and the factors that may affect the thermal insulation properties of a material.
To test the effectiveness of different materials as thermal insulation:
1. Place a small beaker inside a larger beaker on a heatproof mat.
2. Add 100cm^3 of boiled water to the small beaker.
3. Place a cardboard lid on the large beaker with a hole for a thermometer. Ensure the thermometer is in the water but not touching the beaker.
4. Record the initial temperature using the thermometer and start the stopwatch.
5. Record the temperature every 2 minutes for 20 minutes.
6. Repeat with different materials to fill the space between the small and large beaker.
7. Subtract the final temperature from the initial temperature to get the temperature change, the material with the largest change is the least insulating.
To test how the thickness of material affects the thermal insulation:
Same method, but wrap the small beaker with increasing layers of insulation secured by a rubber band.
Systematic error: zero error on measurement of volume device.
Random error: parallax error on thermometer, incorrect volume measurement, incorrect timings
Hazards: beakers, hot water
Risks: cuts, burns, scalds
Prevention: keep beaker in centre of workspace, clean broken glass, let equipment cool, eye protection
Equation for efficiency + definition of high efficiency.
Useful output/total input. Efficiency: a higher proportion of the energy input is usefully transferred.
What are the nine energy resources and are they used for transport, electricity generation or heating?
Fossil fuels and biofuel are used for all three.
Geothermal and solar are used for heating and electricity generation.
Nuclear, wind, hydroelectric, waves and tides are used for electricity generation.
What are the 8 energy stores and 4 types of energy transfer.
Kinetic, thermal, chemical, magnetic, electrostatic, nuclear, GPE, EPE.
Mechanical, heating, electrical, radiation (light and sound).
