Reducing Unwanted Energy Transfers
No description yet. This curated deck is ready for daily study.
Card preview (7)
Describe two ways you can reduce unwanted energy transfers.
• Lubrication reduces energy transferred by friction • Thermal insulation reduces the rate of energy transfer by heating
(Exam-style question) A woman is cycling in a race. Before the race, she puts oil on the bike chain. Explain why putting the oil on the bike chain increases the efficiency of the woman’s cycling.
The oil acts as a lubricant, which reduces the energy lost due to friction
What is conduction?
The process which transfers energy through an object
State what is meant by thermal conductivity.
How well a material transfers energy by conduction
Metals have a high thermal conductivity and gases, such as air, have a low thermal conductivity. Describe the difference between high and low thermal conductivity.
• The lower the thermal conductivity of a material, the slower the rate of energy transfer through it • The higher the thermal conductivity of a material, the faster the rate of energy transfer through it
Describe how the factors of thermal conductivity and thickness affect how quickly a building cools.
• A building that has walls with a low thermal conductivity will cool more slowly • A building with thick walls will cool slowly, given that the thicker a wall is, the slower the rate of energy transfer
(Exam-style question) A builder is trying to minimise the rate at which a house cools. Explain one way the builder could reduce the rate at which the house cools.
• They could use cavity walls, which are made up of an inner and an outer wall with an air gap in the middle • The air gap reduces the amount of energy transferred by conduction, because air has a very low thermal conductivity