(c)Which is the energy-saving light bulb and which is the filament bulb?

A

B

Do this now!

(a)What are these diagrams called?

(b)How efficient is each light bulb?

Title: EfficiencyKey Question: How can we improve

the efficiency of Wall E?

Friction between the moving parts

causes heatingThe 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!

Wall E is happier now he is more efficient!

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.

Industry tries to capture

and use heat.

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)PipeSilver 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.