Efficiency of Machines Flashcards
Why do we call it wasted heat?
Because we can’t do anything useful with it.
What is useful energy?
Concentrated energy.
The entire energy output by a machine both useful and wasted, ends up as what?
Heat.
Where is the heat transferred to?
Cooler surroundings, which then becomes warmer.
What happens when the heat is transferred to cooler surroundings?
The energy becomes less concentrated.
It dissipates.
What happens the energy?
The total amount stays the same.
It just becomes increasingly spread out.
The spread out energy can not be what?
Easily used or collected back in again.
What do you need to think about when choosing appliances?
The cost-effectiveness and efficiency.
EXAMPLE.
A low-energy bulb is what?
About 4 times as efficient as an ordinary light bulb.
EXAMPLE.
What is a energy-efficient light bulb?
A more expensive light bulb that lasts longer.
EXAMPLE.
If an energy-saving light bulb was £3 and saved £12 a year, what would be it’s payback time?
3 months.
EXAMPLE.
Compare energy saving light bulbs and ordinary light bulbs?
More efficient than low-energy light bulbs.
Last longer.
EXAMPLE.
Disadvantage of energy-saving light bulbs?
Expensive.
Don’t give out as much light as the other two types of bulb.
New, efficient appliances are what?
Cheaper to run than old, less efficient appliances.
How do you work out the cost-effectiveness of a new appliance?
Need to work out its payback time.
Sometimes what can ‘waste’ energy be?
Actually useful.
What do heat exchangers do?
Reduce the amount of heat energy that is ‘lost’.
How do heat exchangers reduce the amount of heat energy that is lost?
By pumping a cool fluid through the escaping heat.
What happens to the temperature of this fluid?
Rises as it gains heat energy.
The heat energy in the fluid can be then what?
Converted into a form of energy that’s useful again.
Either in the original energy or other useful functions.
EXAMPLE.
Heat from the car’s engine can be transferred to what?
The air to warm up passenger compartment.
