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Speed of electron

  1. Mar 16, 2012 #1
    How fast does an electron travel in a typical direct circuit? F. example; In a flashlight.

    And... Is the speed constant?

  2. jcsd
  3. Mar 16, 2012 #2


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    Science Advisor

    No, electrons moving through a direct current circuit move much slower than the speed of light. How fast an electron moves depends upon both voltage difference and resistance. Specifically, I= RV where I is the current (in amps), R is the resistance in Ohms, an V is the voltage difference (in volts). To calculate the the speed of electrons, reduce the current from amps to "electrons per second" through the current an divide by the length of the circuit.
  4. Mar 16, 2012 #3


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    The electrons in a conductor will move approximately near the Fermi velocity I believe. For copper, this is less than 1% of the speed of light. This speed is not constant, either, and is subject to statistical considerations (some move slower). One thing to note is that while the electrons move at tremendous speeds, they are not all moving in the same direction. The overall velocity, called the drift velocity, is on the order of millimeters per second. This is analogous to how, even on a calm down, air molecules are themselves moving around at hundreds of meters per second despite having little or no overall velocity.
  5. Mar 18, 2012 #4
    The speed of an electron will approach but never reach the speed of light (c).
    The definition of the speed of an electron in a wire, is current. So unless the current of a given device to use your example, a flashlight, is moving at a speed of 299792458m/s it is not exceeding the speed of light.
    And yes the speed is constant.

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