User's Manual

15
012-04695D Thermal Radiation System
Data and Calculations
① Calculate R, the resistance of the filament at each of the voltage settings used (R = V/I).
Enter your results in Table 3.1.
② Use the procedure on pages 3 and 4 of this manual to determine T, the temperature of the
lamp filament at each voltage setting. Enter your results in the table.
③*Calculate T
4
for each value of T and enter your results in the table.
④*On a separate sheet of paper, construct a graph of Rad versus T
4
. Use Rad as your dependent
variable (y-axis).
*In place of calculations ① and , some may prefer to perform a power regression on Rad
versus T to determine their relationship, or graph on log-log paper and find the slope.
Questions
① What is the relationship between Rad and T? Does this relationship hold over the entire
range of measurements?
② The Stefan-Boltzmann Law is perfectly true only for ideal, black body radiation. A black body is
any object that absorbs all the radiation that strikes it. Is the filament of the lamp a true black
body?
③ What sources of thermal radiation, other than the lamp filament, might have influenced your
measurements? What affect would you expect these sources to have on your results?
a = 4.5 x 10
-3
K
-1
T
ref
(room temperature) = _______ K (K = °C + 273)
R
ref
(filament resistance at T
ref
) = ________Ω
V I Rad R T T
4
(Volts) (Amps) (mV) (Ohms) (K) (K
4
)
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
11.00
12.00
Table 3.1
Data Calculations