Electric Field of Non-Conducting Sheets.

by dvsumosize
Tags: electric, field, nonconducting, sheets
 P: 12 1. The problem statement, all variables and given/known data 3 Infinitely large non conductiong sheets are uniformly charged with surface charge densities Sigma1 = +2x10^-6c/m^2, Sigma2 = +4x10^-6c/m^2, Sigma3 = -5.0x10^-6c/m^2. Distance L = 1.6cm. What is the magnitude and direction of the net electric field at point P? * P | L/2 ________________ Sigma3 | | | 2 *L | ________________ Sigma2 | L | ________________ Sigma 1 2. Relevant equations The only 1 i know of is E = Sigma/(2*εnot) 3. The attempt at a solution Es1 + Es2 + Es3 = Etot at P. So my teacher never really taught us about non-conducting sheets over any distance, and instead told us to google it and ask on forums instead. Please me through how you do this, i can't find a formula that deals with distance between non-conducting sheets.
 PF Patron P: 280 electric fields are added as vectors. just add them with sign.
 PF Patron HW Helper Sci Advisor Emeritus P: 7,077 Use Gauss's Law.
P: 12

Electric Field of Non-Conducting Sheets.

Which formula from that law will i use, the only one i know is the E = Sigma/(2 * e-not)
PF Patron
HW Helper
Emeritus
P: 7,077
 Quote by dvsumosize Which formula from that law will i use, the only one i know is the E = Sigma/(2 * e-not)
That's a result which can be obtained from Gauss's Law.

Gauss's Law: $$\oint_S\vec{E}\cdot d\vec{A}=\frac{q_{inside}}{\epsilon_0}$$
 P: 12 Cramster tells me what i did at the beginning was right, distance doesn't matter in this case. Why did none of you tell me so?
 PF Patron HW Helper Sci Advisor Emeritus P: 7,077 It's rather hard to read your mind well enough to know what you do & don't understand.
 PF Patron P: 280 distance doesn't matter here, as electric field is independent of distance for uniformly charged infinite sheet.
 P: 12 I see.
 PF Patron P: 280 so did you get the answer?
 P: 12 yeah
 P: 118 the same formula sigma/(2epsilon) can be obtained as follows: A Gaussian surface in the form of cylindrical surface can be taken.The field is perpendicular to sheet so only end caps contribute to flux. =>(epsilon)*(sufaceintegral(E.dA))=q =>(epsilon)*(EA+EA)=sigma*A =>(epsilon)*(2EA)=sigma*A canceling A from both sides & rearranging: =>E=sigma/(2*epsilon) Thus for a very large non-conducting sheet distance doesn't matter at all!what matters is sigma.so just as per vectors the electric fields depending upon nature of charge(positive or negative).If negative sigma then E is generally taken as negative(however you can take anything!!!).So the data regarding distance is irrelevant here!!!

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