Find electric field a distance from a charged sheet

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Homework Help Overview

The problem involves calculating the electric field at a distance from a charged sheet, specifically with a given charge density. The context includes a charge density of 5 μC/mm² and a distance of 9 mm from the surface.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the calculation of the electric field using the formula E=σ/2ε0 and express confusion regarding unit conversions from microcoulombs/mm² to SI units. There is also a question about the definition of a "sheet of infinitesimal area."

Discussion Status

The discussion is ongoing, with some participants identifying unit conversion issues and others questioning the terminology used in the problem. Guidance has been offered regarding the need to convert charge density into SI units.

Contextual Notes

There is a noted uncertainty regarding the correct interpretation of the charge density and its implications for the calculation. Participants are exploring the implications of using non-standard units in the context of the problem.

rocapp
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Homework Statement



For a sheet of infinitesimal area, find the electric field 9 mm from the surface if the charge density is 5 μC/mm^2.

Homework Equations



E=σ/2ε0

The Attempt at a Solution



E=(5x10^-6 C/m^2)/(2*8.85x10^-12)

= 2.8 x10^5N/C

I know the correct answer is about 5.6x10^11 N/C, but I'm not sure why. Probably units? I'm not sure how to get N/C at the end when I'm given microcoulombs/mm^2 to begin with. Please help! Thank in advance.
 
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Yes, this is a problem with the units.
You need to convert σ into SI units, ie C/m2
 
(5C/m^2) / (2*8.85x10^-12C/Vm) = 2.82x10^11 V/m
 
rocapp said:

Homework Statement



For a sheet of infinitesimal area, find the electric field 9 mm from the surface if the charge density is 5 μC/mm^2.

Homework Equations



E=σ/2ε0

The Attempt at a Solution



E=(5x10^-6 C/m^2)/(2*8.85x10^-12)

= 2.8 x10^5N/C

I know the correct answer is about 5.6x10^11 N/C, but I'm not sure why. Probably units? I'm not sure how to get N/C at the end when I'm given microcoulombs/mm^2 to begin with. Please help! Thank in advance.
What on Earth is a sheet of infinitesimal area ?
 

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