PHY 114 Lecture 4: Lecture 4
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Ue depends only on the location, not upon the path taken to get there (conservative force) For two point particles take ue = 0 at r = infinity. Electric potential energy (ue) is energy stored in the electric field. For the electric force ue = (cid:3038) (cid:3044)(cid:3117) (cid:3044)(cid:3118) (cid:3045) = (cid:3436)(cid:3038) (cid:3032)(cid:3118)(cid:3045) (cid:3440) A proton and an electron, initially separated by a distance r, are brought closer together. For these two charges, ue = (cid:3436)(cid:3038) (cid:3032)(cid:3118)(cid:3045) (cid:3440) This is like a mass falling near the surface of the earth; positive work is done by the field (work = - u) When q1 and q2 have the same algebraic sign, then ue > 0. This means that work must be done by an external agent to bring the charges closer together (work = - u) (cid:3045) = +(cid:3436)(cid:3038) (cid:3032)(cid:3118)(cid:3045) (cid:3440) Ionizing the atom will strip that atom of its electron. The charge q acts as a source of electric potential.