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Problem about electric resistance

  1. Oct 18, 2009 #1


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    Why electrical resistance can make the current in circuit be constant? When circuit is closed, electric field is built up by the power source (e.g.battery), therefore there should be net force acting on charge carriers and they should accelerate. However, in real case we know that they flow with constant speed. Is that the presence of resistance make them flow with constant speed? What 's the mechanism?
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  3. Oct 18, 2009 #2


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    If we change the power supply (say battery) to a more powerful one. The electric field is stronger in the circuit. But what is interesting is that, though the charge speed is larger, constant speed is maintained no matter how small the resistance is. A tiny resistance can prevent the charge from accelerating!
  4. Oct 18, 2009 #3


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    Well, it sounds like you are thinking about this in terms of what is known as the Drude model, see

    The problem is that the Drude model is wrong in the sense that it is semi-classical and basically assumes the electrons to be small "balls" bouncing around which is simply incorrect (which is why some of the predictions of the Drude model are wrong).

    In order to describe electrical conduction properly you really need a full quantum mechanical description, there is no way to understand it in terms of classical physics.
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