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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Problems with the Young Modulus experiment. watch
- Thread Starter
- 13-10-2009 21:36
- 14-10-2009 06:23
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
- 14-10-2009 14:16
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?