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Current Flow Question.

  1. Feb 19, 2007 #1
    1. The problem statement, all variables and given/known data

    There are 4 diagrams for this questions. Which one do you think it's true?
    (The diagram has a battery with a lightbulb attached to it)

    2. Relevant equations

    N/A

    3. The attempt at a solution

    I think that the current flows from one end to other end but not sure if the current gets weaker or current stays the same.
    I am thinking that the current gets weaker due to the current used to light the lightbulb, which I think it's the way to calculate the voltage.
     
  2. jcsd
  3. Feb 19, 2007 #2
    Current in a wire does not "get weaker" as you go along the wire. If it did, charge would accumulate at some points because it would be moving slow at some points and fast at others.

    Think of it like a pipe of sand with a piston at one end, and a little windmill (sandmill, in this case!) that turns as the sand pushes it. The sand is like the charge carriers (electrons), the windmill is like the light bulb. As we push the piston with constant velocity, the windmill spins, but the current of sand -- basically, the sand per unit time, or sand velocity -- remains the same along the pipe. If it didn't, the sand would continue to bunch up at some points where the current of sand is slower, which doesn't make much sense. The current of sand, therefore, has to be uniform along the pipe.
     
  4. Feb 19, 2007 #3
    So...it should be...
    The electric current is in the direction shown(one end goes through the light bulb and goes back to other end of the battery), and the magnitude of the current is the same in both wires 1(wire before the light bulb) and 2(wire after the light bulb)...?

    So the current stays same even though the current causes the light bulb to light up?
     
  5. Feb 20, 2007 #4
    I will really appreciate if someone can help me with this "simple" problem.
     
  6. Feb 20, 2007 #5
    Can't really help without knowing what you're looking for
     
  7. Feb 20, 2007 #6
    It's basically asking if you attach battery to light the light bulb,
    do you lose the current by lighting up when the current returns after going through the light bulb
    or does the current stay the same throughout the whole circuit?
     
  8. Feb 20, 2007 #7
    Read what Saketh said:

    Current in a wire does not "get weaker" as you go along the wire. If it did, charge would accumulate at some points because it would be moving slow at some points and fast at others.
     
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