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Homework Help: Atomic Theory + Resistance?

  1. Mar 29, 2004 #1
    I have a problem in my book, "Using the atomic theory of matter, explain why the resistance of a material should increase as its temperature increases".

    I can't think of one way that the two relate, but that could be because I don't fully understand what resistance is (on a molecular level). Could anyone help me out? Thanks!
  2. jcsd
  3. Mar 29, 2004 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Yes, you'll have to read up on the microscopic details of resistivity.

    In a nutshell, what happens is this. When a voltage is imposed on a resistor, an electric field is created inside it. This electric field accelerates the electrons, which are bouncing all over due to random thermal motion, giving them a small drift speed. This drift speed, which gives rise to the current in the wire, depends on the average time between collisions for the electrons. The more collisions--the shorter time between collisions--the harder it is to create a current. (Less current = more resistance.)

    By heating the resistor you increase the random motion of the electrons and lattice atoms, increasing the collision rate, and increasing the resistance.

    I hope this helps a little.
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