STUDY OF THERMAL RADIATION LAWS DETERMINATION OF STEFAN CONSTANT

Task 1. Thermoelectromotive force measurement

1.1. Enter the value of thermoelectromotive force at 100 °С into table 1.

1.2. Repeat measurements for furnace temperatures 200, 300, 400, 500 and 600 °С. Enter the results into table 1.

Table 1

1.3. Calculate the absolute furnace temperature as the sum of measured furnace temperature and environment. Enter the results into table 1.

Task 2. Stefan constant determination

2.1. Plot the graph on plotting paper using data from table 2.

Table 2

2.2. Determine furnace radiation power using graph. Enter the results into table 1.

2.3. Determine Stefan constant according to the formula:

Enter the results into table 1.

2.4. Determine deviation of measured value of Stefan constant from table 1:

%

Task 3. Calculation of absolute and fractional errors of Stefan constant determination

3.1. Calculate average value of Stefan constant:

where п = 6 is an amount of measurements.

3.2. Determine deviation of each value from average one:

Enter the results into table 3.

Table 3

Average value of Stefan constant	Deviation from average value	Root-mean square deviation	Student’s coefficient,	Absolute error,	Fractional error, ε, %

3.3. Determine root-mean-square deviations according to the formula:

.

3.4. Calculate the absolute error:

where the Student’s coefficient (α = 0,95 and n = 6).

3.5. Calculate the fractional error:

%

3.6. Write down the result in the following form:

W / (m² К⁴).

Task 4. Stefan law testing using graphical method

4.1. Calculate furnace radiant emittance using data from table 1 according to the formula:

.

Enter the results into table 4.

Plot the graph of the function using data from table 4.

Table 4

Furnace radiant emittance, E, W/m2	lgE			Stefan constant, determined by the graph method, s, W/(m2 К4)

4.3. Calculate the inclination angle tangent of the graph to the x-axis. Make a conclusion about Stefan law confirmation.

4.4. Determine Stefan constant using plotted graph. Compare Stefan constant values obtained by analytical and graphical methods.

Conclusions

The data of laboratory work fulfilment

Pass mark Signature

Mark of laboratory work defence Signature

questions to be admitted for doing laboratory work
and its defending

1. What type of radiation is called thermal radiation?

2. What is the peculiarity of thermal radiation?

3. How does spectral composition of thermal radiation depend on the body temperature?

4. Name energy characteristics of thermal radiation.

5. Formulate Kirchhoff law for thermal radiation.

6. What is a perfectly black body?

7. How can the model of a perfectly black body be given?

8. Draw and explain the graph of function f (λ, Т) for different temperatures of a body.

9. How does wavelength maximum value corresponding to perfectly black body at the increase of body temperature change?

10. Formulate thermal radiation laws for a perfectly black body.

11. What does «violet catastrophe» mean?

12. Formulate principles of the quantum theory of thermal radiation; formulate Planck hypothesis.

13. What is the principal difference between quantum theory of radiation and classical wave theory?

14. Write down Planck formula for thermal radiation.

15. What conclusions follow from Planck formula?

16. Explain the method of experimental determination of Stefan constant applied in this work.

17. How can Stefan law be checked up graphically?

LABORATORY WORK

Date: 2015-01-12; view: 1276