- #1
johnnyboy53
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Homework Statement
I am going through the example problems in the book and it shows me how to find the electric field of a line of charge, which is this
http://imageshack.us/a/img24/8932/img0303fq.jpg
I get to this part where they change ΔQ to (Q/L)ΔY
http://imageshack.us/a/img132/170/img0304lm.jpg
Ok so next question tells me we can treat this thin circle as a line of charge with λ=Q/2∏r
http://imageshack.us/a/img543/9461/img0305wxd.jpg
Then i get to this part again where the ΔQ is involved
http://imageshack.us/a/img27/927/img0306rk.jpg
So why is it that for the ring, ƩΔQ= Q, and for the line of charge, ΔQ must first be converted into (Q/L)Δy? Why didn't we plug in ΔQ= (Q/2∏r)Δy for the ring?
my guess is that for the line of charge, y = L and y was changing for each segment of the portion of E_field we were taking. While for the ring, (Q/2∏r) is constant no matter what segment of E_field we were measuring. Can someone please explain why we substituted ΔQ for the line and not the ring?
Thank you very much in advance
Homework Equations
λ=Q/L
ΔQ=λL = (Q/L)Δy
The Attempt at a Solution
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