Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Electric potential energy Electric potential Conservation of energy Chapter 21 Electric Potential Topics: Sample question: Shown is the electric potential measured on the surface of a patient. This potential is caused by electrical signals originating in the beating heart. Why does the potential have this pattern, and what do these measurements tell us about the heart’s condition? Slide 21-1

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Electric Potential Model Worksheet 2: Energy and Potential in Uniform Fields Rank the change in gravitational potential energy for the following lettered objects in the Earth’s gravitational field. Slide Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. a.. most  _______ _________ ________ ________ _______ _______ ________ b. Explain your ranking, stating why each is greater than, less than, or equal to its neighbors. c. Where is the energy stored? What gains or loses energy as the masses move from one place to another?

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Assembling a square of charges Slide Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley.

Electric Potential Energy Example Problem The electric field between two charged plates is uniform with a strength of 4 N/C. Slide Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. a. Draw several electric field lines in the region between the plates. b. Determine the change in electrical potential energy in moving a positive 4 microCoulomb charge from A to B. c. Determine the change in electrical potential energy in moving a negative 12 microCoulomb charge from A to B.

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Gravitational Potential Energy: Example Problem 2 A spacecraft is launched away from earth Slide Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. a. Draw several gravitational field lines in the region around Earth. b. Determine the change in gravitational potential energy when the spacecraft moves from A to B, where A is 10 million miles from Earth and B is 30 million miles from Earth.

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Electric Potential Energy: Example Problem 3 A small charge moves farther from a positive source charge. Slide Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. a. Draw several electric field lines in the region around the source charge. b. Determine the change in electrical potential energy in moving a positive 4 nC charge from A to B, where A is 3 cm from the source charge and B is 10 cm away. c. Determine the change in electrical potential energy in moving a negative 4 nC charge from A to B.

Slide Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley.

Electric Potential Energy & Electric Potential: Example Problem 4 A proton has a speed of 3.5 x 10 5 m/s at a point where the electrical potential is 600 V. It moves through a point where the electric potential is 1000 V. What is its speed at this second point? Slide Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley.

Example Problem 5 A.The potential at points a and b.The potential difference between a and b. B.The potential energy of a proton at a and b. C.The speed at point b of a proton that was moving to the right at point a with a speed of 4.0 x 10 5 m/s. D.The speed at point a of a proton that was moving to the left at point b with a speed of 4.0 x 10 5 m/s. For the situation shown in the figure, find Slide 21-22

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. A Topographic Map Slide 21-12

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Graphical Representations of Electric Potential Slide 21-13