ENERGY 3 -Energy Transfer

Question 1

What 5 ways could you make your house lose less hear?

Answer 1

1. LOFT INSULATION
2. CAVITY WALL INSULATION
3. HOT WATER JACKET
4. DOUBLE GLAZING
5. DRAUGHT PROOFING

Question 2

What is the payback time for loft insulation?

Answer 2

Initial Cost = £200
Annual saving = £50
Payback time = 4 years (4 x £50)

Question 3

What is the payback time for a hot water tank jacket?

Answer 3

Initial Cost = £15
Annual Saving = £30
Payback time = 6 months

Question 4

What is the payback time for doubling glazing?

Answer 4

Initial cost = £3000
Annual saving = £50
Payback time = 50 years

Question 5

What is the payback time of DRAUGHT proofing?

Answer 5

Initial Cost - £100
Annual saving - £50
Payback time - 2 years

Question 6

What is the payback time of cavity wall insulation?

Answer 6

Initial cost - £500
Annual saving - £70
Payback time - 7 years

Question 7

What is the difference between the most EFFECTIVE method of insulation and the most COST EFFECTIVE method of insulation

Answer 7

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.

Question 8

Explain what is meant by cavity wall insulation and how it works.

Answer 8

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.

Question 9

What is loft insulation and how does it work?

Answer 9

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.

Question 10

Explain draught proofing and how it works?

Answer 10

Strips of foam and plastic around doors and windows stop droughts of cold air blowing in - they reduce hear loss due to CONVECTION.

Question 11

Explain how hot water tank jacket works

Answer 11

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.

Question 12

Explain how thick curtains can reduce heat loss?

Answer 12

This can reduce heat loss through windows through heat loss by CONDUCTION and RADIATION.

Question 13

What is meant by U Value?

Answer 13

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

Question 14

What does SPECIFIC HEAT CAPACITY tell us?

Answer 14

It tells us how much energy stuff can store

Question 15

What is the formula For SPECIFIC HEAT CAPACITY

Answer 15

E = M x C x 0c

Energy Transferred = Mass x Specific Heat Capacity x Temperature Change

Question 16

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?

Answer 16

E
________________________
M x C x Oc

Question 17

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.

Answer 17

E
______________
M x Temp Ch

Specific Heat Transfer = 19,068
____________
0.2 x 105

Answer = 908 J/kg

Question 18

Do you need the same amount of heat energy to increase the temperature of all materials?

Answer 18

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

Question 19

What is the relationship between a material and how much it needs to gain energy to warm up and how it cools down?

Answer 19

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

Question 20

What is SPECIFIC HEAT CAPACITY?

Answer 20

It is how much energy a substance can store

Question 21

What device benefits from having high heat capacities?

Answer 21

Heaters usually have HIGH specific heat capacities so they can store large amounts of heat energy

Question 22

Does water have a high or low specific heat capacity?

Give an example to support your answer.

Answer 22

Water has a REALLY high specific heat capacity. It is for this reason it is pumped around pipes in central heating.

Question 23

Which is a better heater:oil or water?

Answer 23

Water because oils heat capacity is lower than water.

However, oil boils at a higher temperature so oil heaters can produce higher temperatures

Question 24

What are the ine types of energy?

Answer 24

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

Question 25

What three forms of energy are forms of stored energy?

Answer 25

Gravitational Potential, Elastic Potential and Chemical

Question 26

What is the conversation of energy principle?

Answer 26

Energy can be transferred usefully from one form to another, stored or dissipated BUT IT CAN NEVER BE CREATED OR DESTROYED.

Question 27

When is ENERGY ONLY USEFUL?

Answer 27

Energy is only useful when it can be converted from one form to another?

Question 28

Explain the Energy transfer to the following devices:

1. TV
2. Batteries
3. Wind Turbine
4. Firing a Bow and Arrow

Answer 28

1. TV - electrical energy to light, sound and heat
2. Battery - chemical to electrical and heat energy
3. Wind turbine - Kinetic energy to electrical energy
4. Elastic potential energy - kinetic and heat energy

Question 29

What energies are transferred when I type onto my computer and print a age for you to read?

Answer 29

Me thinking (CHEMICAL), me typing (KINETIC), my computer (ELECTRICAL), printing out doument (KINETIC), you reading doc (CHEMICAL)