What is the Electric Flux through a Net in a Uniform Electric Field?

In summary: This was before we learned of potential difference. We just learned about voltage (past high school level physics) today. Thanks :)
  • #1
Sunbodi
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Homework Statement


[/B]
A butterfly net hangs from a circular loop of diameter 400 mm . You hold the loop horizontally in a region where the electric field is 150 N/C downward, as shown in (Figure 1) .
What is the electric flux through the net?
Screen Shot 2017-06-11 at 5.41.34 PM.png

Homework Equations


k = 9E9 N
E = kq/r2
Flux = Q enclosed / E0
Flux = EA

The Attempt at a Solution



r = .195 m

150 = k(q)/(.2)2
q = 6.667E-10

Flux = 6.667e-10/8.85E-12
Flux = 75.3

Mastering Physics says this is wrong. Please help?
 
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  • #2
I'm thinking since this is not a closed surface I should instead simply use Flux = E*A so E = the given amount 150 and A = pi*(.2)^2 giving the amount 18.84 for flux.

I think this is correct however I'm down to only 3 tries. Do you think this is instead correct?
 
  • #3
Sunbodi said:
r = .195 m

150 = k(q)/(.2)2
q = 6.667E-10
This calculation doesn't make any sense to me, since no charge was mentioned. Instead you were given the magnitude and direction of the electric field without any details of the charge distribution that might account for it. You simply need to assume that the field is as given.
Sunbodi said:
I'm thinking since this is not a closed surface I should instead simply use Flux = E*A so E = the given amount 150 and A = pi*(.2)^2 giving the amount 18.84 for flux.

I think this is correct however I'm down to only 3 tries. Do you think this is instead correct?
That would be the correct approach. You want to find the flux passing through the planar surface defined by the loop.

What units will you assign to your flux magnitude of 18.85?
 
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  • #4
Woah,not a closed surface?
Well,then how come you are applying flux=E.A,which comes from Gauss Law,which is only valid for closed surfaces??We are assuming a closed surface(which is in essence the net with a lid on the opening)
Now,since there isn't any charge enclosed in this surface,the total flux passing through this surface ought to be zero.
The rest of the caculation done by you is correct,or rather -18.84 to make the answer perfect.
 
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  • #5
gneill said:
This calculation doesn't make any sense to me, since no charge was mentioned. Instead you were given the magnitude and direction of the electric field without any details of the charge distribution that might account for it. You simply need to assume that the field is as given.

That would be the correct approach. You want to find the flux passing through the planar surface defined by the loop.

What units will you assign to your flux magnitude of 18.85?
N⋅m2/C

Thank you.
 
  • #6
Tanishq Nandan said:
Woah,not a closed surface?
Well,then how come you are applying flux=E.A,which comes from Gauss Law,which is only valid for closed surfaces??We are assuming a closed surface(which is in essence the net with a lid on the opening)
Now,since there isn't any charge enclosed in this surface,the total flux passing through this surface ought to be zero.
The rest of the caculation done by you is correct,or rather -18.84 to make the answer perfect.
Thank you so much!
 
  • #7
Sunbodi said:
N⋅m2/C
Yes, those units are adequate. But you're more likely to see electric flux shown with the equivalent units V⋅m .
 
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  • #8
gneill said:
Yes, those units are adequate. But you're more likely to see electric flux shown with the equivalent units V⋅m .
This was before we learned of potential difference. We just learned about voltage (past high school level physics) today. Thanks :)
 

What is electric flux through a net?

Electric flux through a net refers to the measure of the total number of electric field lines passing through a given surface. It is a way to quantify the strength of an electric field.

How is electric flux through a net calculated?

The electric flux through a net is calculated by multiplying the magnitude of the electric field by the area of the surface and the cosine of the angle between the electric field and the surface normal. This can be expressed mathematically as Φ = E * A * cos(θ).

What is the unit of measurement for electric flux through a net?

The unit of measurement for electric flux through a net is volt meters squared (V·m²), also known as newton meters squared per coulomb (N·m²/C).

What does a positive or negative electric flux through a net indicate?

A positive electric flux through a net indicates that the electric field lines are leaving the surface, while a negative electric flux indicates that the electric field lines are entering the surface. This is determined by the direction of the electric field relative to the surface normal.

What factors can affect the electric flux through a net?

The electric flux through a net can be affected by the strength of the electric field, the size and shape of the surface, and the orientation of the surface relative to the electric field. It can also be affected by the presence of other charges or materials in the surrounding environment.

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