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Homework Help: Two identical droplets of water... [Potential]

  1. Sep 16, 2015 #1
    1. The problem statement, all variables and given/known data
    Suppose you have two identical droplets of water, each carrying charge 7.92 pC spread uniformly through their volume. The potential on the surface of each is 144 Volts.

    Now, you merge the two drops, forming one spherical droplet of water. If no charge is lost, find the potential at the surface of this new large water droplet. in V.

    2. Relevant equations
    I don't have any equations since it's "water droplet" with no specified shape.

    General formula for potential due to a single point charge is V = kq/r
    3. The attempt at a solution
    Is this question easy or tricky? Shouldn't the answer be 144 + 144 = 288 V? Due to conservation of charges?
  2. jcsd
  3. Sep 17, 2015 #2


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    Staff: Mentor

    Which shape do you expect for a droplet without contact to anything else?
    What is the potential from such an object?
    It is not tricky, but it is not as easy as adding two numbers.
    Charge is conserved, but that does not mean you can just add potentials.
  4. Sep 17, 2015 #3

    rude man

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    The new droplet of water has what radius, assuming sphericity? What total charge? Ergo, what potential?
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