PASCO TD-8564 THERMAL EFFICIENCY APPARATUS - Manual (Page 14)

Thermal Efficiency Apparatus 012-05443A
10
➄ Connect the 2
Ω
load resistor with a short patch cord as shown in Figure 1.1. Connect a voltmeter
across the load resistor. The choice of the 2
Ω
load resistor is arbitrary. Any of the load resis-
tances may be used.
Procedure
➀ Allow the system to come to equilibrium so that the hot and cold temperatures are constant.
This may take 5 to 10 minutes, depending on the starting temperatures. To speed up the
process, increase the voltage across the heating resistor momentarily and then return it to
the original setting. If it is desired to cool the hot side, the voltage can be momentarily
decreased. Remember that the thermistor resistance goes down as the temperature increases.
➁
Measure the temperature resistances of the hot side and the cold side by using the toggle
switch to switch the ohmmeter to each side. Record the readings in Table 1.1. Convert the
resistances to temperatures using the chart on the front of the device or Table 1 as explained
in the Measurements section and record these temperatures in Table 1.2.
➂
Record the voltage (V
H
) across the heating resistor, the current (I
H
), and the voltage across
the load resistor (V
W
) in Table 1.1.
➃
Lower the voltage across the heating resistor by about 2 V.
➄ Repeat Steps 1 through 4 until data for five different hot temperatures have been taken.
Calculations
➀ For each of the data runs, calculate the power supplied to the hot reservoir, P
H
, and the
power used by the load resistor, P
W
, and record these in Table 1.2.
➁ Calculate the temperature difference for each trial and record it in Table 1.2.
➂
Calculate the actual efficiencies from the powers and record in Table 1.2.
➃ Calculate the Carnot (maximum) efficiencies from the temperatures and record in Table 1.2.
Table 1.1 Data for Heat Engine
Trial T
H
(k
Ω
) T
c
(k
Ω
) T
H
(°C) T
H
(°C) V
H
I
H
V
w
1
2
3
4
5