Problems with the Young Modulus experiment.

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Acta Non Verba
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#1
Report Thread starter 12 years ago
#1
Yo,

I'm doing an experiment write up for the young modulus. The value for the young modulus I got was far off from the true value, but I think this was expected.

What I want to know is the problems that can occur during a standard classroom experiment that could effect the results and the calculation of the young modulus.

Problems I've talked about so far:
- We took the diameter once at the start of the experiment, but the wire might not be uniform and its diameter may change during the experiment
- errors in reading, zero error, etc.
- errors with equipment used

There's another error about kinks in the wire, but I'm not sure how to word it..

Thanks in advance for any help =].
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genghiz9000
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#2
Report 12 years ago
#2
you're probably using "engineering" stress and strain to calculate E..thats where majority of the error comes from.
Actual stress and strain takes into consideration the decreasing of the diameter(or the cross section area) of the rod/specimen during the application of the load.
of course true stress/strain is much more complex to deal with than engineering stress/strain

btw, i did this stuff in school the past few weeks
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CJN
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#3
Report 12 years ago
#3
For the diameter of the wire, use a micrometer to measure the diameter of the wire say in 5 different places down the length of the wire and find an average.

Also, doing it in very hot or cold temperatures will affect the results.

For kinks in the wire when you measure the original length of the wire hang it up and put a light weight on it (not so much that it stretches) but enough to pull it down to get rid of any kinks.

What values did you have and what was your final E?
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RibsCoull
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#4
Report 11 months ago
#4
Thanks!-From 11 years in the future.
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