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Before starting the experimental run, wait for a few
minutes before taking the temperature of the
calorimeter block.
Switch on the heater and start the clock.
Wait until the temperature has risen about 20
record the time and final temperature.
The specific heat capacity can then be calculated from the
equation:
(
I
U
t
m
c
.
.
=
.
.
0
− 0
2
with I: current, U: voltage, t: time, m: mass of calori-
meter block, c: specific heat capacity,
temperature,
: final temperature
0
2
6. General notes
6.1 Explanation of how to minimise the error
Assuming that the readings for the current and voltage
are reasonable accurate, the two main sources of error
in the experiment will be the readings of the
temperature change and the effects of any heat loss.
Obviously the heat loss will depend on the excess
temperature above the room temperature, so this can be
minimised by keeping the temperature rise as small as
possible.
o
)
1
: initial
0
1
U33020
4
0 0 1 2
.
A
0...5 A
0...20 V
Fig. 1 Experimental set up
Subject to technical amendment
© Copyright 2008 3B Scientific GmbH
If the thermometer can only be read accurately to 1
then a temperature rise of 10
error, which is really too large for this type of
experiment. Therefore, it is a balance between the
error introduced by a large temperature increase
C and
causing heat losses, and a small temperature
increase giving a large percentage error in the
temperature readings. A 20
give a 5% error in reading the thermometer
(assuming it can only be read accurately to 1
reasonable low error due to heat loss.
6.2 Rumford's correction
Rumford argued that heat losses could be eliminated
by the following process. If the metal block is kept in a
fridge for several hours before the experiment, then it
will start at, say,
temperature after the experiment was
temperature, then the heat it took in while below room
temperature would be equal to the heat it gave out
while above room temperature, so there would be no
heat loss.
0
.
V
would give a 10%
o
rise in temperature will
o
below room temperature. If its final
0
0
,
o
) and a
o
above room
