Physics Help Forum Electrical images method

 Mar 17th 2014, 01:18 PM #1 Junior Member   Join Date: Mar 2014 Posts: 1 Electrical images method This is the theory for a laboratory session. If we have two hollow cylinders, one with radius r1 and the other with radius r7, the center of the first one being placed at a distance d from the center of the second one, what are the surfaces having the same electric potential? The cylinder with radius r7 is connected to the ground, while the cylinder with radius r1 is charged. I should find a way to replace the cylinders with "lines", or if we look at a section, replace the circles with two points. The book says they use the electrical images method, but I've never studied it. Can you please explain how they arrived at those three relations in the attached picture? I know how to find the electrical image of a single charge inside a grounded sphere, but the "inside circle" is not the ordinary charge. Thank you! Attached Thumbnails
 Mar 18th 2014, 09:45 AM #2 Senior Member     Join Date: Apr 2008 Location: Bedford, England Posts: 668 I am guessing that the images method is indicating that the surface of the grounded cylinder can be treated as a "mirror" when calculating the electrical potential.
Mar 23rd 2014, 09:36 PM   #3
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 Originally Posted by Razvan This is the theory for a laboratory session. If we have two hollow cylinders, one with radius r1 and the other with radius r7, the center of the first one being placed at a distance d from the center of the second one, what are the surfaces having the same electric potential? The cylinder with radius r7 is connected to the ground, while the cylinder with radius r1 is charged. I should find a way to replace the cylinders with "lines", or if we look at a section, replace the circles with two points. The book says they use the electrical images method, but I've never studied it. Can you please explain how they arrived at those three relations in the attached picture? I know how to find the electrical image of a single charge inside a grounded sphere, but the "inside circle" is not the ordinary charge. Thank you!
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 Tags electrical, images, method