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 Advanced Electricity and Magnetism Advanced Electricity and Magnetism Physics Help Forum Jan 24th 2010, 09:48 AM #1 Junior Member   Join Date: Jan 2010 Posts: 3 Electric Field of a Uniformly Charged Ring 1. The problem statement, all variables and given/known data A uniformly charged ring of radius 8.1 cm has a total charge of 118 micro Coulombs. The value of the Coulomb constant is 8.98755e9 N M^2/C^2. Find the magnitude of the electric field on the axis of the ring at 1.15 cm from the center of the ring. Answer in units of N/C. 2. Relevant equations F= k Qq/ r^2 E= kq/r^2 3. The attempt at a solution I tried subtracting 1.15 cm from 8.1 cm for "r" and plugged that "r" value in the F equation but that answer is wrong. By axis , do they mean horizontally (as in along the diameter) or vertically?Someone said I had to integrate but I dont know what to integrate and from what points.   Jan 24th 2010, 11:09 AM   #2
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 Originally Posted by ILoveCollege 1. The problem statement, all variables and given/known data A uniformly charged ring of radius 8.1 cm has a total charge of 118 micro Coulombs. The value of the Coulomb constant is 8.98755e9 N M^2/C^2. Find the magnitude of the electric field on the axis of the ring at 1.15 cm from the center of the ring. Answer in units of N/C. 2. Relevant equations F= k Qq/ r^2 E= kq/r^2 3. The attempt at a solution I tried subtracting 1.15 cm from 8.1 cm for "r" and plugged that "r" value in the F equation but that answer is wrong. By axis , do they mean horizontally (as in along the diameter) or vertically?Someone said I had to integrate but I dont know what to integrate and from what points.
Hi ILoveCollege and welcome to PHF! It's a very common problem. For instance, I found in google Electric Field on the Axis of Charged Ring or Electric Field Along the Axis of a Charged Semicircle or Ring.
Does it make sense?
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Isaac
If the problem is too hard just let the Universe solve it.   Jan 24th 2010, 12:11 PM   #3
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 Originally Posted by arbolis Hi ILoveCollege and welcome to PHF! It's a very common problem. For instance, I found in google Electric Field on the Axis of Charged Ring or Electric Field Along the Axis of a Charged Semicircle or Ring. Does it make sense?
Yes! Thank You! I also have another question:
"Sketch the gravitational "lines of force" for two equal point masses. These are isomorphic to the electrostatic lines of force of..."
My question is wouldn't two equal "+" point charges produce the same electric field line diagram as two equal "-" point charges?   Jan 24th 2010, 12:17 PM   #4
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 Originally Posted by ILoveCollege Yes! Thank You! I also have another question: "Sketch the gravitational "lines of force" for two equal point masses. These are isomorphic to the electrostatic lines of force of..." My question is wouldn't two equal "+" point charges produce the same electric field line diagram as two equal "-" point charges?
I'll wait for a more experienced person to answer you well on this question. If both lines of force are indeed isomorphic, then I believe that the answer is yes. Now I don't think that they are isomorphic so I have a doubt.
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Isaac
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