In: Physics
Table 1
DATA
CALCULATIONS
L (mm) Rrm (Ω) ΔL (mm) Rhot
(Ω) Trm (C°) Thot (C°) ΔT
(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 ΔT = Thot – Trm. Record the
result in the table.
3. Using the equation ΔL = αL ΔT, calculate α for copper, steel,
and aluminum.
αCu = 1.81556E-05
αsteel =
1.48877E-05
αAl = 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. ΔV = αvol V ΔT)
αCu = ΔL / (L ΔT)
= 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
αvol = 3* αCu
= 3* 1.81556E-05
= 5.44668E-05
For steel
αvol = 3* αsteel
= 3*1.48877E-05
= 4.46631E-05
For aluminium
αvol = 3* αaluminium
= 3*2.53018E-05
= 7.59054E-05