
#1
Mar2311, 01:02 AM

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 nonconducting 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 nonconducting sheets. 



#2
Mar2311, 01:07 AM

PF Gold
P: 280

electric fields are added as vectors. just add them with sign.




#3
Mar2311, 01:47 AM

Emeritus
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PF Gold
P: 7,404

Use Gauss's Law.




#4
Mar2311, 08:29 AM

P: 12

Electric Field of NonConducting Sheets.
Which formula from that law will i use, the only one i know is the E = Sigma/(2 * enot)




#5
Mar2311, 06:24 PM

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PF Gold
P: 7,404

Gauss's Law: [tex]\oint_S\vec{E}\cdot d\vec{A}=\frac{q_{inside}}{\epsilon_0}[/tex] 



#6
Mar2411, 01:15 AM

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?




#7
Mar2411, 01:52 AM

Emeritus
Sci Advisor
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PF Gold
P: 7,404

It's rather hard to read your mind well enough to know what you do & don't understand.




#8
Mar2411, 02:26 AM

PF Gold
P: 280

distance doesn't matter here, as electric field is independent of distance for uniformly charged infinite sheet.




#9
Mar2411, 09:43 AM

P: 12

I see.




#10
Mar2411, 10:52 AM

PF Gold
P: 280

so did you get the answer?




#11
Mar2411, 10:49 PM

P: 12

yeah




#12
Apr1011, 12:50 PM

P: 121

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 nonconducting 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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