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## Physics library

### Course: Physics library>Unit 11

Lesson 3: Electric potential energy, electric potential, and voltage

# Electric potential from multiple charges

In this video David shows how to find the total electric potential at a point in space due to multiple charges. Created by David SantoPietro.

## Want to join the conversation?

• David says that potential is scalar, because PE is scalar -- but vectors must come into play when we place a charge at point "P" and release it?

The calculation for potential at point "P" is +5,250 J/C, so if we place a +1 C charge there, then it will have 5,250 J of PE. Once we place that +1 C charge there and release it, the 5,250 J of PE will convert into KE and the charge will move -- but it will move in a specific, predictable path -- won't it?

How can we determine the path that any charge would take upon being placed in that position? • Can the potential at point P be determined by finding the work done in bringing each charge to that point? • About this whole exercise, we calculated the total electric potential at a point in space (p) relative to which other point in space?
And the final result tells us that a charge of 1 Coulomb on the point p can do 5250J of work ("displacement against a force") more than any other point?
Thanks! • In this video, are the values of the electric potential due to all the three charges absolute potential (i.e. with respect to infinity)?
(1 vote) • Is there any thing like electric potential energy difference other than electric potential difference ? please answer soon . • Sorry, this isn't exactly "soon", but electric potential difference is the difference in voltages of an object - for example, the electric potential difference of a 9V battery is 9V, which is the difference between the positive and negative terminals of the battery.

Electric potential energy difference would be the difference in potential energies at a point in space - but I'm not really sure what it would look like. I doubt you'll ever see the term "electric potential energy difference" anywhere so no need to worry about that :-)
• If i have a charged spherical conductor in side another bigger spherical shell and i made a contact between them what will happen ?
does they balance at equal electric potential ?
or the charge goes to the outer shell ?
and why?
(1 vote) • Why is the electric potential a scalar? Which way would a particle move?
(1 vote) • So if we're trying to calculate a scalar quantity, we plug in signs based on charge. If we're trying to calculate a vector quantity, we plug in signs based on direction. Correct?
(1 vote) • 1. If the distance given in a problem is in cm (rather than m), how does that effect the "j/c" unit (if at all)?
2. If I wanted to calculate how much energy it takes to move one of these charges from its current place to a place a few meters over, could I just say that movement would take the EP measurement of one point (ex: 2,250J/C for V1) times the amount of Coulumbs the point has? AKA: How would I calculate the amount of energy needed to move a point?
(1 vote) • 2. Two point charges each of magnitude q are fixed at the points (0, +a) and
(0, –a) in the Cartesian coordinate system.
i. Draw a diagram showing the positions of the charges.
ii. What is the potential Vo at the origin?
iii. Show that the potential at any point on the x-axis the potential is
given by
   
2 2 2 2
0
0
1 2
4 2
q q V
a x a x  
  
 
iv. At what values of x is the potential one half of that at the origin?
v. Sketch the variation of the potential along the x-axis as a function
of x.
(1 vote) 