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Need help with electricity topic

  1. Jan 23, 2008 #1
    currently we have been studying mechanic physics and the teacher though that it would be fun to do a fun electricity related lab. the lab was to investigate the voltage across a copper resistor and a superconductor when the temperature is brought down with liquid nitrogen. my question is why does resistence increase as temperature increase. everywhere i have searched just tells me this fact but doesn't really explain why.
     
  2. jcsd
  3. Jan 23, 2008 #2

    mgb_phys

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    In simple terms the resistance in metals is due to the free surface electrons being bounced around by the thermal motion of the metal ions. At lower temperatures this motion is reduced so there is less to disturb the free motion of the electrons.

    When you get to very low temperatures it gets more complicated.
     
  4. Jan 24, 2008 #3
    i also have another question. resistance equals roe(l/a). isn't roe the most affected by temperature? but i am not sure why
     
  5. Jan 24, 2008 #4

    mgb_phys

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    Rho is resistivity - which is just a measure of the resistance to motion of electrons in the material for exactly the reasons I just wrote.

    L / A is just a term to include how far they have to go (L) and how much space there is for them to move (A)
     
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