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© Boardworks Ltd 2005 1 of 31 KS4 Physics Energy in the Home.

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Presentation on theme: "© Boardworks Ltd 2005 1 of 31 KS4 Physics Energy in the Home."— Presentation transcript:

1 © Boardworks Ltd of 31 KS4 Physics Energy in the Home

2 © Boardworks Ltd of 31 Contents Energy in the Home Uses of energy Heat loss and insulation Summary activities Saving energy

3 © Boardworks Ltd of 31 How many different uses of energy can you spot? Energy in the home activity

4 © Boardworks Ltd of 31 Uses of energy What are four important uses of energy in our homes? Heating Which one do you think we use the most energy for? Hot water Lighting Cooking

5 © Boardworks Ltd of 31 Uses of energy

6 © Boardworks Ltd of 31 Sources of energy in the home The type of fuel we use to provide our energy at home will depend on many things but nearly all homes rely on a constant supply of electricity. Other fuels can be used for heating, hot water and cooking: What are some of the advantages and disadvantages of these forms of energy? oil gas coal

7 © Boardworks Ltd of 31 Comparing energy cost Using the information in the table below, draw a bar graph that shows the amount of energy (in megajoules, MJ) per pound we get for each energy source. Put the energy sources along the x-axis, and the amount of energy per £ on the y-axis MJ energy per £ ElectricityGasCoalOil

8 © Boardworks Ltd of 31 Comparing energy cost Energy (mJ) per £

9 © Boardworks Ltd of 31 Comparing energy cost What does the graph tell you? Why do you think electricity is used so widely in homes? Electricity generation wastes energy and is expensive compared to the other fuels.

10 © Boardworks Ltd of 31 Contents Energy in the Home Uses of energy Heat loss and insulation Summary activities Saving energy

11 © Boardworks Ltd of 31 Heat loss from houses Most energy is lost through the roof and walls. In houses, energy is lost from the roof, the door, the walls, the windows and the floors. In order to reduce electricity bills and pollution, energy losses must be kept to a minimum.

12 © Boardworks Ltd of 31 Effect of insulation on heat loss

13 © Boardworks Ltd of 31 Reducing heat loss from houses As you go through the next few slides complete the table below to show how various types of insulation prevent heat energy loss from our homes.

14 © Boardworks Ltd of 31 Reducing heat loss – curtains Curtains reduce draughts (convection currents) leaving the house. They are opaque and so don’t allow much radiated heat to pass through them.

15 © Boardworks Ltd of 31 Reducing heat loss – walls This reduces heat loss by conduction through the bricks. Most outside walls have an empty space between the two layers of bricks called a cavity. Cavity wall foam insulation is pumped in-between the bricks to prevent convection within the cavity. convection currents in the cavity foam prevents convection currents

16 © Boardworks Ltd of 31 Reducing heat loss – windows The insulating effect of the gap can be improved further by sucking all the air out to create a vacuum. Double glazing is expensive and difficult to smash without a special hammer. A great deal of energy is lost through windows. By adding an extra pane, the trapped air between the two panes acts as an insulator and reduces heat loss by conduction.

17 © Boardworks Ltd of 31 Reducing heat loss – roof Loft insulation contains trapped air, which forms an insulating layer between the loft and the rest of the house. The air heated by central heating is less dense than the cooler air around it. As a result, warm air rises. The ceilings become heated and eventually the heat escapes through the roof.

18 © Boardworks Ltd of 31 Reducing heat loss – radiators Placing shiny silver-coated card between the wall and the radiator reduces heat loss by radiation by reflecting it back into the room. Radiators heat the wall a great deal – this wastes heat energy.

19 © Boardworks Ltd of 31 Reducing heat loss – draughts Draught excluders are hairy or spongy strips that close gaps and prevent the convection currents escaping. Draughts are convection currents. A great deal of heat energy is lost in this way but it is the easiest type of heat loss to prevent.

20 © Boardworks Ltd of 31 Insulation and heat loss

21 © Boardworks Ltd of 31 Insulation and heat transfer

22 © Boardworks Ltd of 31 The vacuum flask How does a vacuum flask keep hot drinks hot and cold drinks cold? 1. The vacuum between the two layers of glass prevents heat leaving or entering by conduction. 2. The plastic/cork lid is an insulator and prevents convection currents escaping. 3. The silvered walls prevent heat leaving or entering by radiation.

23 © Boardworks Ltd of 31 Contents Energy in the Home Uses of energy Heat loss and insulation Summary activities Saving energy

24 © Boardworks Ltd of 31 Payback time For example: adding silver reflectors behind radiators costs £25 and saves £50 per year. Payback time is how long it takes for the cost of installing insulation to be equalled by the savings from reduced energy costs. payback time = cost to install (years) saving each year Therefore, the payback time = 25/50 = 0.5 years or 6 months

25 © Boardworks Ltd of 31 Calculating payback time 3 years 80 years 1 year 5 years Why is double glazing so popular if the payback time is so long? What is the payback time for these types of insulation?

26 © Boardworks Ltd of 31 Cost-effectiveness Adding silver reflectors behind radiators costs £25 and saves £50 per year. Cost-effectiveness is a comparison of how much insulation costs and how much it can save in reduced energy bills. Cost-effectiveness = saving each year cost to install For example: Cost-effectiveness = 50/25 = 2 Therefore, reflectors are more cost-effective than draught excluders. Cost-effectiveness = 50/50 = 1 Adding draught excluders costs £50 and saves £50 per year.

27 © Boardworks Ltd of 31 Calculating cost-effectiveness

28 © Boardworks Ltd of 31 Contents Energy in the Home Uses of energy Heat loss and insulation Summary activities Saving energy

29 © Boardworks Ltd of 31 Glossary cavity wall – A wall constructed of two layers of bricks with a small air gap in between. This reduces heat loss by conduction. double glazing – Two panes of glass with a small air gap between them, which reduces heat loss by conduction. Sometimes the air is sucked out of the gap creating a vacuum. cost-effectiveness – A comparison of how much insulation costs and how much it can save in reduced energy bills. insulator – A material that is a very poor conductor of heat and so reduces heat loss. payback time – The time it takes for the cost of insulation to be equalled by the savings from reduced energy costs.

30 © Boardworks Ltd of 31 Anagrams

31 © Boardworks Ltd of 31 Multiple-choice quiz


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