reducing unwanted energy transfers

Question 1

explain how you can reduce unwanted energy transfers through lubrication

Answer 1

• when an object moves there is usually at least one frictional force moving against it
• causes energy to be dissipated
• lubricants reduce the friction between the objects’ surfaces when they move
• therefore reducing the amount of energy dissipating

Question 2

explain how you can reduce unwanted energy transfers through cavity walls

Answer 2

• cavity walls (inner and outer wall with an air gap in the middle)
• air gap reduces the amount of energy transferred by conduction through the walls
• can also fill gap with foam (cavity wall insulation) which reduces energy transfer by convection

Question 3

explain how you can reduce unwanted energy transfers through loft insulation

Answer 3

• fibreglass wool often used as it is a good insulator and has pockets of trapped air
• laid across loft floor and ceiling
• reduces energy loss by conduction and helps prevent convection currents from being created

Question 4

explain how you can reduce unwanted energy transfers through double-glazed windows

Answer 4

• have an air gap between the two sheets of glass to prevent energy transfer by conduction through the windows

Question 5

explain how you can reduce unwanted energy transfers through draught excluders

Answer 5

• around doors and windows to reduce energy transfers by convection

Question 6

list 4 ways to reduce unwanted energy transfers in the home

Answer 6

• cavity walls
• loft insulation
• double-glazed windows
• draught excluders

Question 7

explain how you can reduce unwanted energy transfers depending on walls

Answer 7

• have thick walls made from a material with low thermal conductivity
• the thicker the wall and lower conductivity, the slower the rate of energy transfer so building will cool more slowly

Question 8

what is the effect of a high thermal conductivity on the rate of energy transfer by conduction?

Answer 8

the rate is higher