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Conceptual Question about electric potential

  1. Dec 11, 2014 #1
    Guys, i really need help on answering this question.....

    Can a charged particle ever move from a low electric potential to a high electric potential and yet have its electric potential energy decrease? Explain.

    What i think is that, no it is not possible for a charged particle to move to a higher potential and yet have its electric potential energy decrease. This is so because any particle which experiences a positive change in potential cannot have a decrease in electric potential energy.
     
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  3. Dec 11, 2014 #2

    Orodruin

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    Electric potential V is related to potential energy U according to U = QV, where Q is the charge. Can you increase V while decreasing U? If so, what is the condition?
     
  4. Dec 12, 2014 #3
    As far as i am concern electron is a particle which moves from a low electric potential to a high electric potential and yet have its electric potential energy decrease.As it moves naturally from lower to higher potential (no work is done on it, so no increase in potential energy) it's potential energy is converted into kinetic energy as it moves.
     
  5. Dec 12, 2014 #4
    This is not true. If it moves due to the field, there is work done (by the force exerted by the field) and the potential energy decreases.
    The work done by the field is equal to the negative of the change in potential energy. It is also equal to the change in kinetic energy.
    You can think either in terms of work and KE:
    W=ΔKE (work-energy theorem)

    or in terms of KE and PE, replacing W by -ΔPE
    -̶Δ̶P̶E̶=̶-̶Δ̶K̶E̶ ̶o̶r̶ ̶
    -ΔPE=ΔKE or

    ΔPE+ΔKE=0 (conservation of energy)

    The first "picture" (work and KE) is more general. The last one works only for conservative forces, when you can derive the force from a potential.
     
    Last edited: Dec 12, 2014
  6. Dec 12, 2014 #5
    is it right?
     
  7. Dec 12, 2014 #6
    As far as i am concern electron is a particle which moves from a low electric potential to a high electric potential and yet have its electric potential energy decrease.Am i right till here?
     
  8. Dec 12, 2014 #7
    No, I corrected. Just using copy-paste without paying enough attention. :)

    And I think your last statement is correct. Negative particles move from low to high potential. From negative to positive.
     
  9. Dec 12, 2014 #8
    and it's (negative particle for eg.electron) potential energy decreases when it moves from lower to higher potential,right?
     
    Last edited: Dec 12, 2014
  10. Dec 12, 2014 #9
    answer to your question would be electron is a particle which can move from a low electric potential to a high electric potential and yet have its electric potential energy decrease.
     
  11. Dec 13, 2014 #10

    sophiecentaur

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    Electrical Potential is defined in terms of Work done on a Unit Positive Charge (1C), brought from infinity. The Potential Energy of a charge (positive or negative) at a certain position will be relative to some other position and will depend upon its sign and, when it moves to increase or decrease its position in the Potential Field, the sign of the change in its Potential Energy will also be affected by the sign of its charge. This is pretty obvious really if you think of needing to put energy In when you move 'uphill' and getting energy out when you move 'downhill' ; whether it's uphill or downhill (electrostatically speaking) will depend upon the sign of the test charge.
    So, when you are dealing with electrons (-) things will be the other way round from the situation with a unit positive charge.
     
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