User Name Remember Me? Password

 Electricity and Magnetism Electricity and Magnetism Physics Help Forum Sep 21st 2016, 07:53 PM #1 Junior Member   Join Date: Sep 2016 Posts: 3 Electric potential energy of the system of three charges 1: The electric potential energy of two point charges approaches zero as the two point charges move farther away from each other. If the three point charges (two positive, one negative) lie at the vertices of an equilateral triangle, the electric potential energy of the system of three charges is... Answer: negative. 2: The electric potential energy of two point charges approaches zero as the two point charges move farther away from each other. If the three point charges (one positive, two negative) lie at the vertices of an equilateral triangle, the electric potential energy of the system of three charges is... Answer: negative. Why would this be the case? Equation for electric potential energy is, U = K( SUM[qi/ri] ) => U = (q1/r1) + (q2/r2) + (q3/r3) ). By this equation, I understand that the second question would be negative by U = (+q1/r1) + (-q2/r2) + (-q3/r3) ) = -q2/r2. But Looking back at the first question, this doesn't hold. Applying the first line of the question, will leave negative(question1) and positive(question2), so this also doesn't work. What am I missing? Last edited by johnwill8258; Sep 21st 2016 at 08:00 PM.   Sep 22nd 2016, 08:02 AM #2 Senior Member   Join Date: Aug 2008 Posts: 113 #1 ... one negative, two positive charges $\dfrac{k\color{blue}{q}\color{red}{q}}{r} + \dfrac{k\color{blue}{q}\color{red}{q}}{r} + \dfrac{k\color{red}{q}\color{red}{q}}{r}$ $\color{blue}{negative} + \color{blue}{negative} + \color{red}{positive}$ #2 ... two negative, one positive charge $\dfrac{k\color{blue}{q}\color{blue}{q}}{r} + \dfrac{k\color{blue}{q}\color{red}{q}}{r} + \dfrac{k\color{blue}{q}\color{red}{q}}{r}$ $\color{red}{positive} + \color{blue}{negative} + \color{blue}{negative}$ topsquark, mash and Woody like this.  Tags charges, electric, energy, potential, system ,

,

,

,

,

,

,

,

,

,

electrostatic potential energy of a system of 3 charges

Click on a term to search for related topics.
 Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post roshanhero Advanced Mechanics 1 Dec 14th 2013 11:04 AM jasonlewiz Electricity and Magnetism 0 Jul 23rd 2010 10:19 PM uglydaryl Electricity and Magnetism 2 Sep 4th 2009 02:52 AM cerberus Electricity and Magnetism 4 Aug 24th 2009 12:16 PM Rainy2Day Advanced Electricity and Magnetism 0 Feb 9th 2009 03:10 PM