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. Capacitors and Capacitance (Key Equations) Slide Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Capacitance C = |Q| / |Delta V| Property of the conductors and the dielectric Special Case - Parallel Plate Capacitor C = Kappa * Epsilon 0 *A / d Energy Pe e = 1/2 |Q| |Delta V| |Delta V| = Ed
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Capacitors Slide Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Note: Battery is a source of constant potential What happens when you pull the plates apart? With Battery With no Battery What happens when you insert a dielectric? With Battery With no Battery
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Properties of a Current Slide 22-8
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Batteries The potential difference between the terminals of a battery, often called the terminal voltage, is the battery’s emf. Slide ∆ V bat = = W chem q ____
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Definition of a Current Slide 22-9
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Light the Bulb Slide Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Can you light a bulb when you have 1 battery 1 Bulb 1 wire A - yes B - no
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Simple Circuits The current is determined by the potential difference and the resistance of the wire: Slide I = ∆ V chem R _____