Efficiency of Machines Flashcards
What do most energy transfers involve?
Some losses, usually as heat.
Why are useful devices only useful?
Because they can transfer energy from one form to another.
What happens to the useful input?
Its always lost or wasted, often as heat.
The less energy wasted, what does this say about the device?
The more efficient the device is.
The energy flow diagram is what?
The same for all devices.
What is the energy flow diagram?
Energy input in to the useful device.
Useful energy output of the device.
Side - wasted energy - heat and sound.
What is a machine?
A device which turns one type of energy into another.
What is the efficiency of any device defined as?
Efficiency = useful energy out divided by total energy in.
What is the power input and output?
Efficiency = useful power out divided by total power in.
What can you give efficiency as?
A decimal or multiply answer by 100 to get a percentage.
What is the formula triangle for efficiency?
Useful out
Efficiency x Total in
How to use the formula?
Find the total energy in.
Find the useful energy out.
Divide smaller one by bigger to get a value somewhere between 0-1.
REMEMBER THIS.
No device is 100% efficient and the wasted energy usually spreads out as heat.
What are usually 100% efficient?
Electric heaters.
Why are electric heaters 100% efficient?
Because all the electricity is converted to ‘useful’ heat.
All energy ends up as heat energy.
