How do I Calculate V(ab) from E if A(-8,3,2) and B(5,2,3)?

  • Thread starter Thread starter NWNINA
  • Start date Start date
NWNINA
Messages
7
Reaction score
0

Homework Statement


Calculate V(ab) if E = (-5 y / x^3) ax + (5/x) ay + 4 az V/m.
A(-8,3,2) and B(5,2,3).


Homework Equations



Vab=-∫Edl


The Attempt at a Solution



So I tried

V=-[∫(-5y/x^3)dx {from 5 to -8}+ ∫(5x)dy {from 2 to 3} + ∫4dz {from 3 to 2}]

The problem is that the limits are wrong. What should I do?
Should it be the distance and not the literal point on the plane? like the first one, should it be 0 to 13, the second one 0 to 1, the third one 0 to 1?
and what do I do with the remaining variables after the integration. For ex, in the first one I would have a y and on the second one a x
 
Physics news on Phys.org
Check if the electric field is conservative. If it is not, the work between a and b depends on the path, and potential is not defined.

ehild
 
ehild said:
Check if the electric field is conservative. If it is not, the work between a and b depends on the path, and potential is not defined.

ehild

It doesn't say anything about this.
 
Potential exist if the curl of the electric field is zero. Have you heard about that?
If not, check if you copied the formulas for E correctly, or any path is given in the problem. If you were supposed to integral for the path you used, note that when determining the integral for a line segment, the initial and final values of all variables have to been substituted. See figure.

ehild
 

Attachments

  • lineintegral.JPG
    lineintegral.JPG
    9.2 KB · Views: 625
ehild said:
Check if the electric field is conservative. If it is not, the work between a and b depends on the path, and potential is not defined.

ehild

I ended up reading a lot from the book, and yes it is conservative.
The book is just theory no example. So I don't really know the correct approach for this.
I think I'm going to go with V=-[∫(-5y/x^3)dx {from 5 to -8}+ ∫(5x)dy {from 2 to 3} + ∫4dz {from 3 to 2}]

and at the end, where I'm left with variables, substitute them for the coordinates from A
 
Last edited by a moderator:
NWNINA said:
I ended up reading a lot from the book, and yes it is conservative.

The z component of the curl is not zero, so it is not conservative.

NWNINA said:
The book is just theory no example. So I don't really know the correct approach for this.
I think I'm going to go with V=-[∫(-5y/x^3)dx {from 5 to -8}+ ∫(5x)dy {from 2 to 3} + ∫4dz {from 3 to 2}]

and at the end, where I am left with variables, substitute them for the coordinates from A

The integral for the first line segment goes from (5,2,3) to (-8,2,3) (red line in the figure). The second integral goes from (-8,2,3) to (-8,3,3) (the blue line) and so on. You have to substitute the values of all variables.

ehild
 
Back
Top