Reducing unwanted energy transfers Flashcards
(7 cards)
What can be used to reduce friction between objects surfaces when they move
Lubricants
What are lubricants
Usually liquids eg oil, that can flow easily between objects and coat them so that they move past eachother easier
Dissipated meaning
Energy lost to surroundings
What does insulation do
Reduces the rate of energy transfer by heating
Ways to prevent energy lost through heating
-… walls, made from materials with a low … conductivity
—>the slower the building will …
T… insulation:
-c… walls
—> inner and an o… wall with … gaps, these air gaps reduce the amount of … through the walls
-loft …
—>can reduce c… currents being created in lofts
-double-… windows
—>have air … between two … of glass
-thick walls, made from materials with a low thermal conductivity
—>the slower the building will cool
Thermal insulation:
-cavity walls
—> inner and an outer wall with air gaps, these air gaps reduce the amount of conduction through the walls
-loft insulation
—>can reduce convection currents being created in lofts
-double-glazed windows
—>have air gaps between two sheets of glass
Insulation practical
1. Equipment list: … can with lid, n…, k…, t…, t…, m… b…
2. Boil water in a …, pour …ml into can
3. Use a … to measure the … temp of water
4. Place … on the container and leave for … minutes
5. Remove the … and record the … temp
6. Pour away the … and allow to … to room …
7. Repeat this experiment with 2, …, 6, 8 … of newspaper around the …
- Equipment list: metal can with lid, newspapers, kettle, thermometer, timer, mass balance
- Boil water in a kettle, pour 150ml into can
- Use a thermometer to measure the initial temp of water
- Place lid on the container and leave for 5 minutes
- Remove the lid and record the final temp
- Poor away the water and allow to cool to room temp
- Repeat this experiment with 2, 4, 6, 8 layers of newspaper around the can
Equation for efficiency
Useful output/total input x100
