ENERGY 3 -Energy Transfer Flashcards
What 5 ways could you make your house lose less hear?
- LOFT INSULATION
- CAVITY WALL INSULATION
- HOT WATER JACKET
- DOUBLE GLAZING
- DRAUGHT PROOFING
What is the payback time for loft insulation?
Initial Cost = £200
Annual saving = £50
Payback time = 4 years (4 x £50)
What is the payback time for a hot water tank jacket?
Initial Cost = £15
Annual Saving = £30
Payback time = 6 months
What is the payback time for doubling glazing?
Initial cost = £3000
Annual saving = £50
Payback time = 50 years
What is the payback time of DRAUGHT proofing?
Initial Cost - £100
Annual saving - £50
Payback time - 2 years
What is the payback time of cavity wall insulation?
Initial cost - £500
Annual saving - £70
Payback time - 7 years
What is the difference between the most EFFECTIVE method of insulation and the most COST EFFECTIVE method of insulation
Most effective insulation is the one that produces the GREATEST SAVING of money each year.
Most COST EFFECTIVE tends to be the cheapest as the PAYBACK TIME tends to be much QUICKER.
Explain what is meant by cavity wall insulation and how it works.
Foam is squirted into the gap between the bricks (in a house there’s an outer brick wall and another inner brick wall with an air gap in between).
The foam stops CONVECTION currents being set up in the gap and radiation across the gap.
The foam also has air pockets (air is an insulator) also helps reduce heat loss by CONDUCTION.
What is loft insulation and how does it work?
Loft insulation is a thick layer of fibreglass wool laid out across the whole loft floor reduces CONDUCTION and RADIATION into the roof space from the ceiling.
Explain draught proofing and how it works?
Strips of foam and plastic around doors and windows stop droughts of cold air blowing in - they reduce hear loss due to CONVECTION.
Explain how hot water tank jacket works
Hot water tank jacket consists of putting an insulating material such as fibreglass wool around the hot water tank.
This then prevents heat loss through CONVECTION.
Explain how thick curtains can reduce heat loss?
This can reduce heat loss through windows through heat loss by CONDUCTION and RADIATION.
What is meant by U Value?
U Value is a rating for how effective a material is at insulating.
The better the insulator the lower the U value.
U value of a typical duvet is 0.75 W/m2k
What does SPECIFIC HEAT CAPACITY tell us?
It tells us how much energy stuff can store
What is the formula For SPECIFIC HEAT CAPACITY
E = M x C x 0c
Energy Transferred = Mass x Specific Heat Capacity x Temperature Change
If you use the FORMULA for SPECIFIC HEAT CAPACITY and you want to work out something other than ENERGY TRANSFERRED what does the formula look like?
E
________________________
M x C x Oc
Applying the Formula Triangle what is the answer to the following question?
An empty 200g aluminium kettle cools down from 115c to 10c losing 19,068 Joules heat energy.
What is the specific heat capacity of aluminium.
E
______________
M x Temp Ch
Specific Heat Transfer = 19,068
____________
0.2 x 105
Answer = 908 J/kg
Do you need the same amount of heat energy to increase the temperature of all materials?
No - heat energy varies from material to material.
It takes 4200 J to warm 1kg of water by 1c but only 139J to warm 1kg of mercury by 1c
What is the relationship between a material and how much it needs to gain energy to warm up and how it cools down?
Material that takes a lot of energy to warm up also releases loads of energy when they cool down - they store a lot of heat
What is SPECIFIC HEAT CAPACITY?
It is how much energy a substance can store
What device benefits from having high heat capacities?
Heaters usually have HIGH specific heat capacities so they can store large amounts of heat energy
Does water have a high or low specific heat capacity?
Give an example to support your answer.
Water has a REALLY high specific heat capacity. It is for this reason it is pumped around pipes in central heating.
Which is a better heater:oil or water?
Water because oils heat capacity is lower than water.
However, oil boils at a higher temperature so oil heaters can produce higher temperatures
What are the ine types of energy?
NEGLECT ‘K”
NUCLEAR - released only from nucleur reactions
ELECTRICAL - whenever a current flows
GRAVITATIONAL POTENTIAL - anything that falls
LIGHT - from the Sun, light bulbs
ELASTIC POTENTIAL - stretched springs, elastic, rubber
CHEMICAL - processed by foods, fuels, batteries
THERMAL - flows from hot objects to colder ones
KINETIC - aything that’s moving has it
