Table 1 DATA CALCULATIONS L (mm) Rrm () L (mm) Rhot () Trm (C°) Thot (C°) T (C°)

Question

Table 1                              
                              
   DATA               CALCULATIONS          
L (mm)   Rrm ()   L (mm)   Rhot ()   Trm (C°)   Thot (C°)   T (C°)  
Copper 699   112 0.79 9.2 22.5   84.75 62.25  
Steel 699   112 0.64 9.437 22.5   84 61.5  
Aluminum 699   112 1.07 9.767 22.5   83 60.5  
                              
1. Use the Conversion Table at the end of the 'Instructions' section, or the one on the top of the expansion base, to convert your thermistor resistance measurements, Rrm and Rhot, into temperature measurements, Trm and Thot. Record your results in the table.                                
                              
                              
     2. Calculate T = Thot – Trm. Record the result in the table.                              
                              
3. Using the equation L = L T, calculate for copper, steel, and aluminum.                              
                              
Cu =   1.81556E-05               steel =   1.48877E-05      
                              
Al =   2.53018E-05                          

1. Look up the accepted values for the linear expansion coefficient for copper, steel, and aluminum. Compare these values with your experimental values. What is the percentage difference in each case? Is your experimental error consistently high or low?                                
                              
   2. On the basis of your answers in question 1, speculate on the possible sources of error in your experiment. How might you improve the accuracy of the experiment?                               
                              
                              

       3. From your result, can you calculate the coefficients of volume expansion for copper, aluminum, and steel? (i.e. V = vol V T)                                
                              
                              

Explanation / Answer

Cu = L / (L T)

= 0.79 / (699*62.25)

= 1.815559807E-05

accepted values for the linear expansion coefficient for copper is 17E-06

% error = { [ 1.81556E-05 ] - [ 1.7E-05 ] } / 1.7E-05

= 6.797 %

accepted values for the linear expansion coefficient for steel is 13E-06

% error = [ (1.48877E-05) - (1.3E-05) ] / 1.3E-05

= 14.52 %.

accepted values for the linear expansion coefficient for aluminium is 24E-06

% error = [ (2.53018E-05) - 2.4E-05 ] / 2.4E-05

= 5.424%

The experimental errors are consisitently low.

2)

The possible sources of error can be:

a) error on the part of the accuracy of the thermisor

b) Human error in noting down the values like measuring the change in length, temperatures etc.

c) error on the part of the accuracy of the scale used to measure the length of the rods.

the accuracy of the experiment can be improved by careful performance of the experiment, with proper observations and using more accurate exquipment.

3)

For copper

vol = 3* Cu

   = 3* 1.81556E-05

= 5.44668E-05

For steel

vol = 3* steel

= 3*1.48877E-05

= 4.46631E-05

For aluminium

vol = 3* aluminium

= 3*2.53018E-05

= 7.59054E-05

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