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Static Electricity

  1. Aug 27, 2014 #1
    I was reading that if a balloon is rubbed against cloth, it becomes charged and therefore it sticks to a wall for a short time if I place it against a wall. So how come if I have a non-static charge (current charge) and then I placed small bits of paper besides it, the paper doesn't stick as well.

    Sorry if my question sounds idiotic, I just need to clear up some conceptions
     
  2. jcsd
  3. Aug 27, 2014 #2
    What causes the balloon to stick to the wall is the charges on the surface of the balloon to be attracted to the wall via an electric field. In the case of a charge current, the number of + and - are roughly equal, so there is no electric field (thus no attraction/repulsion).
     
  4. Aug 28, 2014 #3
    Can you explain what you mean by + and - being equal in a current?
     
  5. Aug 28, 2014 #4

    Drakkith

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    Staff: Mentor

    By "current charge" do you mean the current flowing in a circuit?
     
  6. Aug 28, 2014 #5
    Yes.
     
  7. Aug 29, 2014 #6
    Current is the flow of electrons, which we define as negative charge -- this the symbol " - ". Protons are positive charge " + ". In an atom of copper (neutral charge), the number of protons = number of electrons.

    A circuit wire is made of of copper (or some other conducting medium). So the number of electrons = number of protons in the wire. Of course, this is not exactly true because there is a "sea" of electrons flowing along the conductive band of the copper lattice when the electricity is flowing. This is why I say + and - are "roughly equal": because it is impossible to say which electron belongs to which atom of copper (they are all flowing!).

    So long story short, the number of + and - are roughly equal in the circuit wire so there is NO external electric field generated. However, if you place 2 such conducting wires next to each other, they will push apart or pull together. Do you know why?
     
  8. Aug 29, 2014 #7

    Drakkith

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    Staff: Mentor

    Applying a voltage to a circuit causes current to flow through the circuit. But no charges actually leave the circuit, so it stays neutral. It's like water flowing around a loop of pipe. The water flows, but no water leaves the pipe.
     
  9. Aug 30, 2014 #8
    @Aichuk

    When u rub the balloon, u are creating a charge imbalance (if u rub balloon to your hair, i think the balloon gains electrons from your hair and becomes negatively charged .. but it doesn't really matter if it gains or loses, what matters is.. this creates a charge imbalance).. and its this charge imbalance that is responsible for the "static cling"

    However when u have an electric current in a wire, there is no charge imbalance in the wire, the wire is NEUTRAL (its only that there is a flow of either negative or positive charges in one particular direction ), so there will not be any static cling

    Static electricity is all about the charge imbalances and its the physics of the SURFACE of a conductor

    Current electricity is all about motion of charges and its usually the physics of the current INSIDE a conductor
     
  10. Aug 30, 2014 #9
    Besides the circuit not being charged, are the small bits of paper charged? You haven't said if you rubbed them against cloth or not. In either case they, of course, don't stick.
     
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