Physics Help Forum What is the electrostatic energy between two charged plates?

 Electricity and Magnetism Electricity and Magnetism Physics Help Forum

 Feb 28th 2018, 07:20 PM #1 Junior Member   Join Date: Feb 2018 Posts: 10 What is the electrostatic energy between two charged plates? Electrostatic energy = kq1q2/r Or U = qE?
 Mar 1st 2018, 07:00 AM #2 Senior Member   Join Date: Apr 2015 Location: Somerset, England Posts: 1,009 The energy stored in an electric field is 1/2 QV Can you do your questions now or do you need more help? Last edited by studiot; Mar 1st 2018 at 07:14 AM.
 Mar 1st 2018, 08:00 AM #3 Junior Member   Join Date: Feb 2018 Posts: 10 Why the formula that one? Not kq1q2/r ? Or Ue = qE What change is V Is V = $$\Delta$$ kq/r Last edited by helly123; Mar 1st 2018 at 08:08 AM.
Mar 1st 2018, 08:29 AM   #4
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 Not kq1q2/r ?
Well that is the formula for the force exterted between two charges and you asked about energy.

and this one is the potential energy of a single charge in an existing electric field.
You do not have such charges.

 Or Ue = qE

 Mar 1st 2018, 08:32 AM #5 Junior Member   Join Date: Feb 2018 Posts: 10 Thank you. Then, P = 1/2 QV What can influence the V? Last edited by helly123; Mar 1st 2018 at 08:34 AM.
Mar 1st 2018, 09:32 AM   #6
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 Originally Posted by helly123 Electrostatic energy = kq1q2/r Or U = qE?
The forum rules require that you show us what you've tried before we can help you.

Until then let me ask you what other problems that you've done in this portion of your course, such as other problems with capacitors and the energy stored in them.

Do you know the expression for the energy stored in a capacity or the energy density in an electric field? Do you know the difference between the potential energy associated with two charged particles and the energy stored in an electric field?

 Mar 1st 2018, 04:17 PM #7 Junior Member   Join Date: Feb 2018 Posts: 10 Energy stored in capasitor = 1/2 QV V is amount of energy per charge V = E/q = Ed d is distance traveled parallel to electric field. I am not sure which is d..
 Mar 3rd 2018, 07:41 AM #8 Junior Member   Join Date: Feb 2018 Posts: 10 I found out electrical potential (V) for capacitor usually V = Ed Can i substitute that V to 1/2QV So ratio of Electrostatic energy 2 and 1 Is QEd2/QEd1 = d/2d = 1/2 Is it right?
 Mar 5th 2018, 08:57 AM #9 Senior Member   Join Date: Oct 2017 Location: Glasgow Posts: 303 I don't think that's right. You're comparing a situation where the total distance between the plates is d in one case and 2d in the other, which is not quite the situation you have. I think it would help you if you find the answer to this question: Q: what happens to electrons in the conductor when being placed under the electric field? topsquark and helly123 like this.

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