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Voltage in an open circuit.

  1. Jan 24, 2012 #1
    Hi guys,
    I have recently started to think about basic electronics and realized that I dont know electricity theory at all cause I couldn't answer a few questions asked by my friend.

    Imagine an open circuit(forum_pic)

    Wiill there be any current at all. I understand that when the switch is opened, the circuit is considered to be opened and in opened circuit there is no place for a current.

    why there is no voltage drop on the resistor when there is no current. I understand that Ohms law tells us that if the current is 0 then the voltage drop is zero. U=IR = 0*R= 0
    But i dont understand this on atoms and electrons scale. Could you please explain it to me.

    What about current that will charge switch right contact. Does it act as a cap?

    Attached Files:

    Last edited: Jan 24, 2012
  2. jcsd
  3. Jan 24, 2012 #2


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    Staff: Mentor

    Any two conductors with a gap between them do act like a capacitor, but not a very large one. The twin lead electric cord that goes to an appliance contributes some capacitance across the mains, but it is so small as to be of no consequence at typical mains frequency. It might be significant if you wanted to use the switch in a high quality audio circuit.
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