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Understanding the potential

  1. Oct 11, 2016 #1
    1. The problem statement, all variables and given/known data
    I dont exactly conceptually understand what the potential is. The electric field is a vector at a given point from the charge that describes the strenght and the direction of the fields. Potential is given as a potential of a point in referenve to another point in spave? I have uploaded the picture od a segment of my lecture today where it discribes that there exists a constant in the potential formula which dissapears when we introduce the potential difference..
    2. Relevant equations
    3. The attempt at a solution

    Can someone give a little insight in what it is if you understand what i mean? The potential of a point A is known but the potential of A' is potential of point A plus some constant which is electric field line integral from R to R'. How is that constant if R' is arbitrarily chosen?
     

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  3. Oct 11, 2016 #2

    BvU

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    Hi there,

    Are you familiar with the gravitational potential ?
     
  4. Oct 11, 2016 #3
    Kinda.. it is property of a gravitational field at some point in space..right? I know the expression but dont get the concept..
     
    Last edited: Oct 11, 2016
  5. Oct 11, 2016 #4

    BvU

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    I meant the simpler version: potential energy = mgh. The difference in potential energy only depends on the difference in height, not on the path taken to get from the one height to the other.

    Basically a conservative force is the derivative of a potential.

    the potential of A' is potential of point A plus some value which is electric field line integral from R (position of A) to R' (position of A').

    So R' is not arbitrarily chosen but the path from A to A' can be arbitrarily chosen.
     
  6. Oct 11, 2016 #5
    So lets say we have a charge ##q## and a point ##A## in space whose potential is ##V_A=\frac{Q}{4πε_or_A}## where ##r_A## is the vector from ##Q## to ##A## .If the above is also true for ##B## but with ##r_B## then the potenital defference between these two is some value ##V_{B-A}=\frac{q}{4πε_or_{B-A}}## What good is this expression? What use do we have of this? The potential difference between those two points..?
     
  7. Oct 11, 2016 #6

    BvU

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    If A has ##
    V_A=\frac{Q}{4πε_or_A}## and B has ##
    V_B=\frac{Q}{4πε_or_B}## then the potential difference between these two is of course $$
    V_B - V_A = \frac{Q}{4πε_or_B} - \frac{Q}{4πε_or_A}$$
    Which is the energy per charge needed to bring a charge from A to B
     
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