Energy resources and energy transfers Flashcards
Conservation of energy
Energy can never be created properly destroyed
8 different energy stores
Kinetic
Thermal
Chemical
Gravitational potential
Elastic potential
Electrostatic
Magnetic
Nuclear
4 ways energy can be transferred
Mechanically
Electrically
By heating
By radiation
The law of conservation of energy
Total energy input = useful energy output + wasted energy
How to calculate the efficiency of energy transfer
efficiency =( useful energy output / total energy output ) × 100
Describe this energy transfer : A ball rolling up a slope
Energy is transferred mechanically from the kinetic energy store to its gravitational potential energy store.
Some energy is transferred mechanically to the thermal energy store (due to friction ) and then by heating to the thermal energy stores of the surrounding - this energy is wasted
What is conduction
The process in solids where vibrating particles transfer energy from their kinetic energy store to the kinetic energy stores of their neighboring particles.
Practical to demonstrate conduction
Equipment: clamp stand, metal bar, beads, bunsen burner
- Attach the bead to the metal bar using wax ( leave a space in between each)
- Hold the metal bar with the clamp stand
- Using bunsen burner, heat the side of the bar (with no beads)
- The wax holding the beads will gradually melt, and the beads will fall as the temp increases, starting with the bead closest to the point of heating
What is convection
The molecules in a fluid move from an area of high to low thermal energy while transferring energy
Explain the process of convection
• When a part of a fluid is heated, the particles gain energy and move apart
• These particles become less dense and rise up
•Denser (cooler) particles fall down to take their place
• This repeats until the fluid is all the same temperature
• Creates a convection current
What is thermal radiation
•can also be called infrared radiation
•does not require a medium
•higher temperature and greater surface area = more infrared radiation emitted
• black dull material = best emmiters
• white shiny material = best absorbers
How to reduce the rate of energy transfer
Coduction and convection = Insulation
• clothes, blankets, foam cavity wall insulation
Radiation = colors and surfaces
• shiny white surfaces
Formula for work done
Work done = force × distance moved
What is power
the rate at which energy is transferred
formula for power and the units
power = work done/time
watts, W
