Reducing Unwanted Energy Transfers Flashcards
How can you reduce the amount of energy that’s wasted?
- Lubrication
- Thermal insulation
What happens if you decrease the amount of wasted energy?
A higher proportion of the supplied energy is transferred to useful stores, so the efficiency of the process is increased.
How does lubrication reduce energy transferred by friction?
For objects that are touching each other, lubricants can be used to reduce the friction between the objects’ surfaces when they move.
Usually, what state are lubricants?
Lubricants are usually liquid (e.g. oil), so they can flow easily between objects and coat them.
What is the process of conduction?
- When one side of an object is heated, the particles in the hotter part vibrate more and collide with each other.
- This transfers energy from their kinetic energy stores to other particles, which then vibrate faster.
- This transfers energy through the object.
What is thermal conductivity?
How well a material transfers energy by conduction.
Name an example of a material that has a HIGH thermal conductivity.
Metals.
Name an example of a material that has a LOW thermal conductivity.
Gases (like air).
In a building, why is a low thermal conductivity useful?
The lower the thermal conductivity of its walls, the slower the rate of energy transfer through them (meaning the building will cool more slowly).
What are cavity walls?
Made up of an inner and an outer wall with an air gap in the middle.
Why do some houses have cavity walls?
The air gap reduces the amount of energy transferred by conduction, because air has a very low thermal conductivity.
Other than cavity walls, what other type of walls help reduce the amount of energy transferred by conduction?
Thicker walls - the thicker the wall, the slower the rate of energy transfer.
