PASCO TD-8558A THERMAL EXPANSION APPARATUS - Manual (Page 8)

Thermal Expansion Apparatus 012-04394C
4
between the lug and the tube.
Place the foam insulator over the thermistor lug as shown in Figure 3.
➄ Plug the leads of your ohmmeter into the banana plug connec-
tors labeled THERMISTOR in the center of the expansion base.
Measure and record R
rm
, the resistance of the thermistor at room
temperature. Record this value in the table.
Use tubing to attach your steam generator to the end of the
copper tube. Attach it to the end farthest from the dial gauge.
➇ Use a book or a block of wood to raise the end of the expansion
base at which steam enters the tube—a few centimeters is
sufficient. This will allow any water that condenses in the tube
to drain out. Place a container under the other end of the tube to
catch the draining water.
➈ Turn the outer casing of the dial gauge to align the zero point on the scale with the long
indicator needle. As the tube expands, the indicator needle will move in a counterclockwise
direction.
➉ Turn on the steam generator. As steam begins to flow, watch the dial gauge and the ohmmeter.
When the thermistor resistance stabilizes, record the resistance (R
hot
) in Table 1. Also record
the expansion of the tube length (
∆
L) as indicated by the displacement of the indicator on the
dial gauge. (Each increment on the dial gauge is equivalent to 0.01 mm of tube expansion.)
Note that
∆
L is the difference betwen the dial gauge readings.
➤ Repeat the experiment for the steel and aluminum tubes.
Data and Calculations
DATA CALCULATIONS
L (mm) Rrm (
Ω
)
∆
L (mm) Rhot (
Ω
) Trm (C
°
) Thot (C
°
)
∆
T (C
°
)
Copper
Steel
Aluminum
➀ Use the Conversion Table at the end of this manual, or the one on the top of the expansion
base, to convert your thermistor resistance measurements, R
rm
and R
hot
, into temperature
measurements, T
rm
and T
hot
. Record your results in the table.
Figure 3 Thermistor Attachment
Thermistor Lug
Copper Tube
Banana Connectors
Foam Insulator
TABLE 1 Data and Calculations
➃
➅
➆