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

  • Thread starter NWNINA
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In summary, you are trying to find Vab using the line integral of the electric field between two points, A and B. However, because the electric field is not conservative, the work between A and B depends on the path taken.
  • #1
NWNINA
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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
 
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  • #3
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
 
  • #4
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.
 
  • #5
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
 

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  • #6
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
 
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  • #7
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
 

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

What is "Finding V from E"?

"Finding V from E" is a scientific method used to determine the velocity (V) of a moving object, given its initial energy (E) and the external forces acting upon it.

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Knowing the velocity of a moving object is important in many scientific fields, such as physics and engineering. It allows us to understand and predict the motion of objects, and can be used to design and optimize various systems and technologies.

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The equation for "Finding V from E" is V = √(2E/m), where V is the velocity, E is the initial energy, and m is the mass of the object.

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Yes, the equation for "Finding V from E" can be used for any type of object, as long as its initial energy and external forces are known.

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The accuracy of "Finding V from E" depends on the accuracy of the initial energy and external force measurements. If these values are precise, then the calculated velocity will also be accurate. However, there may be other factors such as air resistance or friction that can affect the actual velocity of the object.

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