Electric Flux Through a 1x1x1 cm Box

In summary, the problem involves finding the net electric flux through a 1x1x1 cm box in an electric field of (350x + 150)i N/C, where x is in meters. The formula used is flux = ExAx + EyAy + EzAz, and after substituting 0.01m for x, the answer should be 3.5x10^-4. However, the poster is unsure about the role of the 150 in the expression and why the flux needs to be multiplied by 2. The solution involves calculating the flux through the front and back sides separately and adding them together, being careful with signs.
  • #1
absolutezer0es
14
0

Homework Statement



A 1x1x1 cm box with edges aligned in the xyz-axes is in the electric field E = (350x + 150)i N/C, where x is in meters. What is the net electric flux through the box?

Homework Equations



flux = ExAx + EyAy + EzAz

The Attempt at a Solution



I substituted into the formula above, including 0.01m for x. I get:

flux = [(350*0.01 + 150)(0.01)^2] + 0 + 0 = 0.01535 Nm^2/C

I then multiply by two because the field is coming through the back and front of the box. I'm not getting the answer right though. What am I missing?
 
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  • #2
absolutezer0es said:
I then multiply by two because the field is coming through the back and front of the box.
You cannot just multiply by 2. Calculate the flux through the front and back sides. (They aren't the same.) Then add to get the net flux, being careful with signs.
 
  • #3
Why aren't they the same? Isn't it a cube? Maybe I don't understand the expression (350x + 150)i like I think I do.

Does the expression mean 350x on the way in and 150 on the way out?
 
  • #4
absolutezer0es said:
Maybe I don't understand the expression (350x + 150)i like I think I do.
What's the field at x = 0? (Where one side is.) At x = 0.01? (Where the other side is.)
 
  • #5
I'm still lost. The field at x=0? There are an infinite number of points on x=0, depending on y and z, no? Same at x=0.01.

I mean, the answer is 3.5x10^-4, according to my text. I substituted 0.01m into the expression and multiplied by (0.01)^2. Don't have a clue why though. What happened to the 150?
 
  • #6
absolutezer0es said:
The field at x=0? There are an infinite number of points on x=0, depending on y and z, no? Same at x=0.01.
The field only depends on x. So all points with the same x value have the same field.
 
  • #7
So what does the 150 mean? Does it have anything to do with the problem?
 
  • #8
absolutezer0es said:
So what does the 150 mean? Does it have anything to do with the problem?
Of course it does! 350x + 150 is a function that gives you the magnitude of the electric field at any point. You can't leave out the 150.
 

1. What is electric flux?

Electric flux is a measure of the electric field passing through a given surface. It is defined as the product of the electric field and the area of the surface.

2. How is electric flux calculated?

To calculate electric flux, you need to first determine the electric field passing through a given surface. Then, you multiply the electric field by the area of the surface that is perpendicular to the electric field. This will give you the electric flux through that surface.

3. What is the unit of electric flux?

The unit of electric flux is volt meters squared (V•m^2).

4. Why is the electric flux through a 1x1x1 cm box important?

The electric flux through a 1x1x1 cm box is important because it can help us understand the behavior of electric fields and how they interact with different surfaces. It also allows us to calculate the strength of an electric field passing through a specific area.

5. How does the electric flux change if the size of the box is increased?

If the size of the box is increased, the electric flux through the box will also increase. This is because there will be a larger surface area for the electric field to pass through, resulting in a higher overall electric flux value.

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