A hot rock ejected from a volcano's lava fountain cools from 1100 C to 40.0 C , and its entropy decreases by 950 J/K. How much heat transfer occurs from the rock?
Goals • To calculate the electric potential energy of a group of charges • To know the significance of electric potential • To calculate the electric potential due to a collection of charges • To use equipotential surfaces to understand electric potential • To calculate the electric field using the electric potential Electric potential energy in a uniform field • The behavior of a point charge in a uniform electric field is analogous to the motion of a baseball in a uniform gravitational field. A charge moving in a uniform field • If the positive charge moves in the direction of the field, the potential energy decreases, but if the charge moves opposite the field, the potential energy increases. • If the negative charge moves in the direction of the field, the potential energy increases, but if the charge moves opposite the field, the potential energy decreases. Copyright © 2012 Pearson Education Inc. Electric potential energy of two point charges • The electric potential is the same whether q moves0in a radial line (left figure) or along an arbitrary path (right figure). Copyright © 2012 Pearson Education Inc. Graphs of the potential energy • The sign of the potential energy depends on the signs of the two charges. • The potential energy associated wit0 q depends on the other charges and their distances from q 0 Copyright © 2012 Pearson Education Inc. Electric potential • Potential is pot
