Monday, 8 September 2014

THE TRANSFER OF HEAT ENERGY


            THE TRANSFER OF HEAT ENERGY 


1 Write down the three ways in which heat may he transferred from one place to another.

2 Which of the following is the worst conductor of heat?
                air copper vacuum glass rubber steel

3 How is heat transferred by conduction?

4 Which is the better conductor, a solid rod of copper or a hollow rod of copper of the same length and diameter?

5 Which of the following metals is the best conductor of heat?
     silver   steel   aluminium   copper

6 Why is a thick glass bottle likely to crack if boiling water is poured into it?

7 Why do people wear layers of clothing in the winter and birds fluff up their feathers to keep themselves warm?

8 By what process is heat transferred down a metal rod?

9 A 2p piece and a 1 p piece are placed on a block of wax beneath a heater. Which one will sink into the wax faster and why?

10 Explain the following:
(a) saucepans for use on a hot plate are made with copper bottoms;
(b) these bottoms are made as flat as possible;
(c) the handle of the saucepans are made of wood or plastic,

11 Describe how the conduction of heat was used in the Davy miners lamp.

12 How would you show simply that water was a poor conductor of heat?

13 Why does double glazing reduce the heat loss from a window?

14 What other ways can the heat losses from a house be reduced?

15 If air is a better insulator than polystyrene, why are cavity walls filled with polystyrene foam?

16 Why is the outlet pipe from a hot water tank at the top of the tank?

17 Why is the freezing compartment of a fridge at the top of the fridge?

18 Why is it not vital to have the top of a chest freezer closed all the time?

19 What is the main difference between conduction and convection?

20 What is the main way in which heat is given out by an ordinary house radiator?

21 Write the following surfaces down in order of efficiency of radiation, starting with the one that radiates heat best:-    white    polished black    polished tin   dull black
22 Which of the surfaces would be the best absorber of heat?

23 Which of the surfaces would be the best reflector of heat?

24 How is the effect of heat radiation used in the thermos flask?

25 If glass absorbs heat radiation why does a greenhouse get so hot inside?

26 Find out what is meant by the greenhouse effect when applied to the atmosphere.

27 If a saucepan is to retain heat say whether it should have a black or a shiny surface and explain your answer.

28 Why is it more likely to be a frosty night if the sky is clear than if it is cloudy?

29 A hot cup of tea is left on the table. Explain carefully how you think that heat could be lost from it.

30 If the tea is now poured into a bowl made of the same material as the cup explain how its rate of cooling will be affected.

31 When an electric light bulb is switched on the bulb soon becomes very hot. Why doesn’t it melt if left on for some time?

32 Why do some lampshades limit the wattage of light bulb that should be put in them?

33 If the Earth were to suddenly lose its atmosphere would it:
(a) become colder by day and warmer by night?
(b) become warmer by day and colder by night?

34 How do you think that the amount of heat radiation received from the Sun would alter if the Earth was twice as far away from the Sun as it is now?