Presentation on theme: "(c)Which is the energy-saving light bulb and which is the filament bulb? (a)What are these diagrams called? (b)How efficient is each light bulb?"— Presentation transcript:
(c)Which is the energy-saving light bulb and which is the filament bulb? (a)What are these diagrams called? (b)How efficient is each light bulb?
Title: Efficiency Key Question: How can we improve the efficiency of Wall E? Friction between the moving parts causes heating The resistance of the wire causes it to get hot when current passes through Sound created when Wall E moves Air resistance causes energy to be lost to the surroundings Lubrication! Streamlined Shape! Tighten bolts! Use wider wires!
Like all machines, even when made more efficient, Wall E still loses heat to the surroundings. Why is it classed as waste energy? Why is it so difficult to use? It heats up the surroundings, and spreads further and further away from the source.
Exam Style Question (about two topics) The efficiency of a heating system in a house depends upon how much heat is lost. Explain why water pipes are often wrapped with the following material. (4) Pipe Silver Foil Foam (bubbles represent trapped air)
Mark Scheme Silver foil causes any heat lost by radiation (1) to be reflected (1) back into the pipe. Heat loss by conduction (1) is stopped through the foam because conduction cannot happen through the trapped air (1).
End of Chapter Questions Only do 1,2,3 and 5. Do not do 4 and 6. We will finish off on Friday.