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Homework Help: Electric potential & potential difference

  1. Jun 9, 2008 #1
    1. The problem statement, all variables and given/known data

    There is no problem but I am trying to understand the definition of 'electrical potential.' What is it. What is electrical potential difference. It is the amount of work needed to move a charge from point A to point B divided by the magnitude of the charge. What is this supposed to mean? Please give any examples. What does it mean that there is '20V worth of potential.'
  2. jcsd
  3. Jun 9, 2008 #2
    This isn't a formal answer. But I like to think of electricity and voltage the same way as gravity and mass. Current always wants to move from higher to lower potential. Like a rock wants to move from larger height to lower height if you drop it. If a large amount of electric charge is at a high potential, it has alot of potential energy (positive or negative depending on the sign of the charge). Just like a large mass at great height also has a large potential energy.
    Last edited: Jun 9, 2008
  4. Jun 9, 2008 #3

    So electrical potential energy is the energy that a charge has when it is at a certain location in an electric field. Just a like rock would have above the earth.

    But what is electric potential & electric potential difference. I am pretty sure electric potential isn't the same as electric potential energy. And electric potential difference, which is it? I am confused indeed.
  5. Jun 9, 2008 #4
    If you lift a rock with mass m a height h it has the energy mgh. Now If you divide by m you get just gh. What is this? This is a number saying how "hard" it generally is to lift something on earth. It would be different on other planets since they have different g. Gravitational potential is a property of the gravitaitional field generated by the planet. Potential energy is a property of a specific mass lifted on the planet.

    If you move a charge (mass) q through a potential difference (height) U it gets the energy q*U. Divide by q and you get just U. This is a number saying how hard it generally is to to move a charge in the electric field. Electric potential is a property of the electric field which some source is generating. Electric potential energy is a property of the specic charge moving in the field.

    Electric potential really is similar to height, it's just that we are so used to height that it can be hard to make the connection between the two. Hope this made it clear :)
    Last edited: Jun 9, 2008
  6. Jun 9, 2008 #5


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    Electrical potential difference is the change in electric potential between two given points.

    Electric potential is the e.p. difference between a given point and some assumed reference point. The location of the reference should be clear from the context of the problem.

    Electric potential energy is simply the energy or work it takes to move a known charge between two locations.

    Electric potential is the e.p. energy per unit charge. It's a useful concept, since for a given electric field or charge configuration, the electric potential does not depend on the value of the charge you might choose to move between the two locations.
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