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Homework Help: How the resistance of a strain gauge attached to a piece of wood varies with the temp

  1. Apr 3, 2008 #1
    hi ive just been given this piece of coursework which is the latest(2008) version and im just wondering if I could get any help on this? thnx! :cheesy grin:

    The manufacturers of wood floors need to know how much the wood expands and contracts with changes in humidity and temperature. One way of detecting expansion or contraction is to use a strain gauge.
    You are required to design a laboratory experiment to investigate how the resistance of a strain gauge attached to a piece of wood varies with the temperature of the wood.
    You should draw a diagram of the apparatus, and in your account you should pay particular attention to:
    (a) the procedure to be followed
    (b) how the strain gauge would be attached to the wood
    (c) the range and precision of any instruments that would be used
    (d) the factors that would need to be controlled to ensure that it is a valid test
    (e) any safety precautions you would take when carrying out the experiment
    (f) particular features of the design that would ensure the accuracy and reliability of your results

    any help on this would be great!
  2. jcsd
  3. Apr 3, 2008 #2
  4. Apr 10, 2008 #3
    I'm doin' this one too...
  5. May 6, 2008 #4
    I'm also doing this one, although I have no idea where to begin :confused:
  6. May 10, 2008 #5
    please , i need some help


    I`ve got the same physics planning exercise and now i am totally confused and I do not know what to do.
    I was thinking about attaching my foil strain gauge to piece of wood and then to set up guarter bridge circuit where on resistor would be at the same resistance like foil strain gauge and the another two resistors will be at the same resistance to each other, then circuit will be balanced and voltmeter reading will be zero.But only two wires will be connected in series to gauge.
    With different effects of temperature, strain gauge will be tensed, so its resistance will change...but my problem is , I really dont know how to measure resistance then with different temperature...i just dont get it...it makes me so sad, cos im trying already for a long time...

    Please help me someone, also i dont know how to change temperature of wood, i think i would need at least 5 different temperatures...

    Thanks for help:smile:
    Last edited: May 10, 2008
  7. May 11, 2008 #6
    Guys??? could you somebody look at it please, i urgently need your help.Thanks again.
  8. May 11, 2008 #7
    I'm doing the same thing.. Stuck on the same issue about resistance.. and also temperature.. How can you measure the temperature of the wood..?

    I am going to heat my wood by using a lab oven
  9. May 11, 2008 #8
    Where would the wires go if its in the oven?......

    Plus shouldnt you be using a wheatstone bridge not a quarter bridge...?

    Im stuck on the same part...temperature as well

    Isnt there any component that can be attached to a surface of a metal used to heating the wood to detect temperature?
  10. May 11, 2008 #9
    Hello !
    Could I set up just simple electric circuit instead of that quarter-bridge strain gauge one?
    Can I just connect my foil strain gauge to power pack, and just connect ampmeter to circuit, also voltmeter around my strain gauge?
    I then i would use only simple formula like R=V/I to calculate my resistance with increasing temperatures.
    Is it possible in the case of electric circuit with the strain gauge?
  11. May 11, 2008 #10
    You heat the wood up first.. Remove it from the lab oven, obviously wearing oven gloves (can be talked about in the safety precautions) then connect the wood into your circuit and measure the readings you need.. You need a range of temperature readings.. Read the question again:
    Design an experiment to investigate how resistance of a strain gauge attached to a piece of wood varies with the temperature of the wood
  12. May 11, 2008 #11
    From my research i know that the change in reistance from the strain gauge is small so its pretty hard to measure it lol....you definatly need the wheatstone bridge so that it can sense small changes in resistance since it somehow amplifies the small resistance into a voltmeter reading or something....

    This planning is like impossible...the school proberbly need to buy new equipment to measure this...since we're only allowed to use avaible school lab equips


    But how would you know the temperature of the wood as it drops? Stick a themometer up it? lol
  13. May 11, 2008 #12
    I'm not sure if that would really work tbh.. Don't think it would be balanced.. But then again i'm not sure
  14. May 11, 2008 #13
    Thats what some people said.. But it sounds stupid.. I'm not sure about it.. But yeah the cicuit you use should amplify the small resistance into a voltmeter reading which can then be used to calculate resistance by R=V/I
  15. May 11, 2008 #14
    You know what im just gona stick a themometer in the wood and heat it up on a bunsen burner......

    the planning is so hard i just hope the experiements aint this hard lol....
  16. May 11, 2008 #15
    Lol just make sure you don't burn your wood into ashes..
    We aren't going to be doing this experiment for our actual thing.. According to my teacher
  17. May 12, 2008 #16
    Yeh i am doing this planning exercise too, you don't actually do the experiment, it's just a plan which goes with the rest of your practical exam, which are different experiments to the one we are planning in this exercise.
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