Connect with us

Electrical Resitance

Discussion in 'Electronic Design' started by [email protected], Jan 9, 2013.

Scroll to continue with content
  1. Guest

    To what extent does the electrical resistance of a metal depend on its temperature?
     
  2. TTman

    TTman Guest

    Ever heard of Google ?
     
  3. Gee that's kind of a broad question. Do you have any particular metal
    in mind?

    For pure metals at high temperatures the resistivity is roughly linear
    with temperature. (A high temperature being defined as being greater
    than the Debye temperature for that material.)

    George H.
     
  4. It varies, by metal, purity, alloy, and temperature range (as well as
    other factors such as annealing and external stresses and magnetic
    field). Pure metals tend to increase more-or-less linearly with
    temperature, around room temperature. Most (not all) alloys have lower
    tempco than pure metals around room temperature. At very cold
    temperatures more dramatic things tend to happen. For example:

    https://encrypted-tbn1.gstatic.com/...iTvGR0sqDDWt7EZCRmZQSnhldly_xAzJo13-cxj_4H71w

    or vs. temperature with under strong magnetic fields:-

    http://ars.els-cdn.com/content/image/1-s2.0-S0011227598000034-gr14.gif


    Or it might drop suddenly to exactly zero, depending. For example, I'm
    told that if you cool U238 to 2.4 K and squish it enough (1.2GPa) the
    resulting alpha phase will go superconducting.

    Here is an interesting paper:-

    http://tinyurl.com/afzzbsf
     
  5. mkr5000

    mkr5000 Guest

    of course he has smartass.

    maybe everyone should just Google it and ignore newsgroups?
     
  6. mkr5000

    mkr5000 Guest

    and besides, both John and Spehro give better answers that anything you can Google. we're lucky they're active on this group.
     
  7. Guest

    I'm assuming the test has ended and it's safe to pass this on:

    See the video
     
  8. Guest

    Actually that's not a good answer for people in the business of purity testing of metals by means of resistivity, tempco, and thermoelectric properties. They're expecting absolutely wild deviations with just parts per gazillion impurity concentrations...
     
  9. Guest

    LOL- I'll concede a 'good'- but 'excellent' would be a stretch.
     

  10. Chuckle*, No one will every accuse you of being overly modest.

    I like knowing it's goes as ~T, then the change with T goes as about 1/
    T
    So I'd guess +0.33% at 300K.
    (Alloy's are just screwed up metals from a 'certain' physics point of
    view.)


    George H.
    *(I trust you will take this in the good spirit in which it is
    offered.)
     
  11. Cool, Do you use some folded design to keep the pick-up out?

    I been thinking about these little diode temp sensors.

    I worry about sticking different metals together,
    it's not clear to me when I get 'battery/chemical action'
    between two metals.

    With the diodes I was thinking about wetting a bit of Al
    and sticking the collector of a transistor to that.
    There's then this Al/solder/transistor-lead sandwich.

    George H.
     
  12. This is a nice graph
    http://www.copper.org/resources/properties/cryogenic/images/Electrical-Resistivity.gif

    From copper.org
    There's lots of other graphs... I don't get the magneto-resistance
    one.

    George H.
     
  13. Sjouke Burry

    Sjouke Burry Guest

    cut
    Well, then you should NOT use diodes, because they stick all sorts of
    metal and semiconductors together.
     
  14. Guest

    I'm just not following what that has to do with temperature dependence?
     
  15. What might happen to the specific resistance of pure Pb when you
    increase the temperature by a couple of °C, from, say, 4.2K to 6.2K?


    Best regards,
    Spehro Pefhany
     
  16. Phil Allison

    Phil Allison Guest

    "mkr5000"
    ** The OP is a very obvious troll - so TTman's reply is both appropriate &
    polite.

    OTOH, yours was totally smartarses and pig arrogant.


    ** When Google likely has the needed info - then that is where to go first.

    OTOH - you can go straight into hell.



    ..... Phil
     
  17. Hi John, I think Spehro was 'commenting' on your "Without exception"
    statement.
    If you'd said, "In general", instead....

    George H.
     
  18. Guest

    But all of the expensive wire is "oxygen free". ;-)
     
  19. Ralph Barone

    Ralph Barone Guest

    So it increases by 3%, then :)
     
  20. LOL


    Best regards,
    Spehro Pefhany
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-