P1.6/7/9 - Energy Dissipation, Efficiency, Power Flashcards
Useful energy
Energy transferred to where it is wanted in the way that it is water
Wasted energy
The energy that is not usefully transferred
Dissipated
- spread out
- lost to the surroundings and stored in a less useful way
Input energy
The energy supplied to the device
Useful output energy
The useful energy transferred by the device
Formula for input energy
Input energy = useful output energy + wasted energy
Formula for efficiency
Efficiency = useful output divided by total input
The greater the percentage of energy that is usefully transferred…
The more efficient it is
How can machines be made more efficient
Through lubrication
-to prevent friction between moving parts
Power is …
The rate of energy transfer
Power supplied
-the energy you supply to a motor per second
The more powerful an appliance is…
The faster the rate of energy transfer is
Units of power
Watts, joules, Kw
1 watt = 1 joule per second
1 kilowatt = 1000 watts
Formula for power
Power = energy transferred divided by time taken for energy to be transferred
Output power
The useful energy per second transferred by it
