version H28986 2014
Cool the cylinder to its original temperature and supply the same amount of heat electrically, using
the heater measured via the joulemeter. Again record the temperature rise and compare the
results.
Further applications:
Simple determinations can be made of the efficiency of electromechanical systems:
1.
An electric motor raising a known weight through a measured distance.
2.
A falling weight driving a generator and lighting a lamp. Note that the final kinetic energy of the
weight may be significant.
Suitable components:
Motor/Generator unit
Lineshaft unit
Lamp unit
Power supply, 6V d.c.
Specific Heat Capacity
Apparatus:
Joulemeter/Wattmeter
Immersion Heater 12V 42W
Aluminium Block, 1kg
Copper Block 1kg
Steel Block 1kg
Thermometer -10° to +110°C Power
supply, 12V 5A d.c. or a.c.
Procedure:
Record the initial temperature of the aluminium block.
Heat the block for about five minutes and measure the electrical energy supplied, W. Record the
final temperature allowing for thermal lag, i.e. note the highest temperature reached after the
heater is switched off.
Repeat the procedure for the other blocks (which have the same mass), supplying the same
amount of energy each time, measured by the joulemeter.
The experiment is intended to provided a quantitative illustration of specific heat capacity, with a
minimum of calculation. With suitable refinements, more precise determinations are possible.
Further applications:
1.
Simple electrical determinations can be made of specific latent heats of fusion and
vaporisation.
2.
In all standard methods of electrical calorimetry, the joulemeter replaces ammeter,
voltmeter and clock, with the advantage that current and p.d. need not remain constant during the
experiment.
