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Homework Help: Closing of switch in series circuit

  1. Oct 18, 2005 #1
    If an ammeter is connected to the negative terminal of a battery,so it is on the opposite end of the line from where the current leaves the battery and enters the circuit,right?So Why, in a series circuit, the meter needle jumps to it's full value instantaneously with the closing of the switch ?

    is this answer right : because of the high value of the differential potential ?
     
  2. jcsd
  3. Oct 18, 2005 #2

    ranger

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    This always confuses me. Doesnt current leave from the negative side and enter the positive. Since current = flow of electron, and electrons = negative. Wouldnt it make sense to say the current flows from the negative side?
     
  4. Oct 18, 2005 #3
    Current was discovered long before electrons. Electron flow explains current, but current had already been defined as the rate of change of net positive charge. So it is a matter of hard-to-overturn convention. (Just think - protons could have been defined as negative and electrons positive!!!)

    Otherwise, the OP's question is a rewording of the old: "why does the light come on as soon as I press the switch?" The flow of current is not equal to the flow of individual particles within it, since the movement of an electron at one end of a wire will cause the next electron to start moving (by electrostatic repulsion), and the next, and the next, all the way to the other end of the wire. As a result, the net flow of charge is a lot greater than individual electron velocities which are, by comparison, snail-paced.
     
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