PASCO TD-8555 THERMAL RADIATION SYSTEM - Manual (Page 9)

5
012-04695D Thermal Radiation System
Experiment 1: Introduction to Thermal Radiation
EQUIPMENT NEEDED:
— Radiation Sensor, Thermal Radiation Cube — Window glass
— Millivoltmeter — Ohmmeter.
ä NOTES:
① If lab time is short, it's helpful to preheat the cube at a setting of 5.0 for 20 minutes before
the laboratory period begins. (A very quick method is to preheat the cube at full power
for 45 minutes, then use a small fan to reduce the temperature quickly as you lower the
power input. Just be sure that equilibrium is attained with the fan off.)
② Part 1 and 2 of this experiment can be performed simultaneously. Make the measure-
ments in Part 2 while waiting for the Radiation Cube to reach thermal equilibrium at each
of the settings in Part 1.
③ When using the Radiation Sensor, always shield it from the hot object except for the few
seconds it takes to actually make the measurement. This prevents heating of the thermo-
pile which will change the reference temperature and alter the reading.
Radiation Rates from Different Surfaces
Part 1
① Connect the Ohmmeter and Millivoltmeter as shown in Figure 1.1.
② Turn on the Thermal Radiation Cube and set
the power switch to “HIGH”. Keep an eye on
the ohmmeter reading. When it gets down to
about 40 k
Ω
, reset the power switch to 5.0. (If
the cube is preheated, just set the switch to 5.0.)
③ When the cube reaches thermal equilibrium—
the ohmmeter reading will fluctuate around a
relatively fixed value—use the Radiation
Sensor to measure the radiation emitted from
each of the four surfaces of the cube. Place
the Sensor so that the posts on its end are in
contact with the cube surface (this ensures that
the distance of the measurement is the same for
all surfaces). Record your measurements in the
appropriate table on the following page. Also
measure and record the resistance of the ther-
mistor. Use the table on the base of the cube to
determine the corresponding temperature.
④ Increase the power switch setting, first to
6.5, then to 8.0, then to “HIGH”. At each
setting, wait for the cube to reach thermal equilibrium, then repeat the measurements
of step 1 and record your results in the appropriate table.
1
2
3 4 5
6
7
8
LOW HIGH
CAUTION: HOT! CA UT
IO N
HO
T!
TH ER MIS TO R
Mo del TD -85 54A
(LE SL IE'S CU BE )
100W
BULB
MAX.
ON
OFF
Millivoltmeter
Ohmmeter
Figure 1.1 Equipment Setup