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Thermal Physics Questions Specific heat capacities:
| copper |
400Jkg-1K-1 |
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| iron |
460Jkg-1K-1 |
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| water |
4200Jkg-1K-1 |
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| ice |
2100Jkg-1K-1 |
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Specific latent heat of fusion of ice = 3·3×105Jkg-1
Molar heat
capacities of a diatomic ideal gas:
Cv = 12·5J(molK)-1 and Cp
= 20·8J(molK)-1
Question
18
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You are given an
uncalibrated
thermometer (that
is, a thermometer
which has no
graduations on it).
Explain how you
would mark a
centigrade scale on
it. |
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Your answer must include definitions of the terms “lower fixed
point” and “upper
fixed point”. |
Question
19
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Metals expand when
they are heated and
contract when they
are cooled. |
a) |
Describe briefly one
problem caused by
the expansion of
metals. |
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b) |
(i) |
What is a “bi-metal
strip”? |
| |
(ii) |
What is a thermostat? |
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(iii) |
Explain briefly how
a bi-metal strip can
be used to make an
electrical
thermostat. |
Question
20
a) |
In what way is the
expansion and
contraction of water
unusual? |
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b) |
State the
temperature at which
water has its
maximum density. |
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c) |
Describe one
problem caused
by the unusual
expansion of water
and one advantage
it brings |
Question
21
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The specific heat
capacity of water is
very high. What
effect does this
have on the weather
conditions
experienced by
people living on
islands? |
Question 22
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Draw diagrams to represent |
a) |
a heat engine |
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b) |
a heat pump (or fridge) |
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On the diagrams, label the work done, w, the energy taken from the source, Q1 and energy given to the sink, Q2. |
Question 23
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Referring to the diagrams of the previous question: write down expressions for the thermodynamic efficiency,
 of |
a) |
a heat engine |
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b) |
a heat pump |
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c) |
a fridge. |
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