Find Energy in Volume Defined by -1<x<1,-1<y<y,-1<z<1

In summary: Ok thanks man yah u are right Wolfram said it was ok.In summary, an electric potential is created in a volume by an electric field. The energy density of this electric field is 2e-9.
  • #1
DODGEVIPER13
672
0

Homework Statement


If V=2x^2+6y^2 V in free space, find the energy stored in a volume defined by -1<x<1,-1<y<y, and -1<z<1. (BTW the < are suppose to less than or equal to or greater than or equal to)


Homework Equations


Upload


The Attempt at a Solution


I am not really sure of the formula here but I assume it needed at triple integral as it gave me 3 sets of limits and a function. Furthermore it asked for a volume so it was the only thing I could think of I relize it is probably wrong but am I even close? If not what formula should I use?
 

Attachments

  • EPSON029.jpg
    EPSON029.jpg
    8.9 KB · Views: 707
Physics news on Phys.org
  • #2
A triple integral is good, but you have to find out what to integrate first.

I'm not sure how to interpret "V=2x^2+6y^2 V", but it looks like an electric potential, so we have an electric field in that volume. What is the energy density of an electric field?
Are you sure there are no units involved?
 
  • #3
Oh sorry yah the V stands or volts so yes it is electric potential. (1/2)(epsilon)E^2 equals energy density of an electric field
 
  • #4
Good, now you can use that to solve the problem.
 
  • #5
So what your saying is that E would equal electric potential here or should I use dV=-Es(dS)
 
  • #6
Thus I would take the derivative of the voltage
 
  • #7
DODGEVIPER13 said:
Thus I would take the derivative of the voltage
That's the idea, right.
 
  • #8
Well what should I derive the function by x or y I'm guessing x
 
  • #9
DODGEVIPER13 said:
Well what should I derive the function by x or y I'm guessing x

x,y, and z, actually. You want to determine the electric field, a vector quantity, by finding the gradient of the potential. Presumably you'll then use the magnitude of this vector in your energy density evaluation (triple integral over the volume).
 
  • #10
Ah ok man thanks so partial derivative with respect to x y and z then integrate that three times with the limits given got it will do later on
 
  • #11
Well the gradient is (4x,12y) if I integrate it straight I get 0 which can't be right . I don't know if it is mathematically legal for me to e the agnitude with the x and y arable still in it but ill try anyway see if that does the trick I gets 101.19288
 
  • #12
Remember that you have to square its magnitude:
DODGEVIPER13 said:
Oh sorry yah the V stands or volts so yes it is electric potential. (1/2)(epsilon)E^2 equals energy density of an electric field
 
  • #13
6e-9
 
  • #14
I got the magnitude to be sqrt(4^2+12^2) which is sqrt(160)=E so then E^2=160 which when I integrate I get 6e-9
 
  • #15
Where epsilon is 8.85e-12
 
  • #16
(4x,12y) depends on x and y, and so does the magnitude. In addition, you are missing the z-component here (it is zero, but you have to include it to get a vector with 3 components).
 
  • #17
I get E=sqrt((4x)^2+(12y)^2)=sqrt(16x^2+144y^2) then E^2=16x^2+144y^2 after integrating I get (1/2)epsilon(1280/3)=2e-9
 
  • #18
Am I ok not trying to rush you just wondering?
 
  • #19
You can check calculations with a computer, so what are you waiting for?
The answer has missing units, but the problem statement has the same problem.
 
  • #20
Ok thanks man yah u are right wolfram said it was ok. I guess I said it wrong did I have the integral set up correctly so that when I performed the integration it would be correct?
 
  • #22
Ok thanks man
 
  • #23
oh hey I know this post is old but I caught a mistake I believe since dV=-E dot dS then the answer shourld be negative 2E-9 also what should the units be Joules?
 
  • #24
You square the electric field, its direction does not matter, and the energy density is always positive.
 
  • #25
Ah yah your right didnt consider that it was squared.
 

1. What does the defined volume of -1

The defined volume represents a cube with sides of length 2 centered at the origin (0,0,0) in 3-dimensional space.

2. How is energy measured in this defined volume?

The energy in this defined volume can be measured using various units such as joules or calories, and can also be measured as potential or kinetic energy depending on the context.

3. What types of energy can be found in this defined volume?

This defined volume contains all forms of energy, including mechanical, thermal, electrical, chemical, nuclear, and electromagnetic energy.

4. How can one calculate the total energy in this defined volume?

The total energy in this defined volume can be calculated by summing up the energy of each individual component within the volume, taking into account any conversions between different forms of energy.

5. What are some real-world applications of finding energy in this defined volume?

There are many real-world applications for finding energy in this defined volume, such as studying the energy distribution in a confined space, determining the efficiency of a system, or predicting the behavior of particles within a given volume.

Similar threads

  • Math POTW for Secondary and High School Students
Replies
1
Views
755
  • Calculus and Beyond Homework Help
Replies
14
Views
636
  • Engineering and Comp Sci Homework Help
Replies
3
Views
1K
  • Calculus and Beyond Homework Help
Replies
2
Views
500
  • Calculus and Beyond Homework Help
Replies
21
Views
2K
Replies
2
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
1
Views
1K
Replies
7
Views
2K
Replies
5
Views
1K
  • Precalculus Mathematics Homework Help
Replies
10
Views
1K

Back
Top