How to Use This Presentation

1. How to Use This Presentation • To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” • To advance through the presentation, click the right-arrow key or the space bar. • From the resources slide, click on any resource to see a presentation for that resource. • From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation. • You may exit the slide show at any time by pressing the Esc key.

2. Resources Chapter Presentation Visual Concepts Transparencies Sample Problems Standardized Test Prep

3. Chapter 17 Electrical Energy and Current Table of Contents Section 1 Electric Potential Section 2 Capacitance Section 3 Current and Resistance Section 4 Electric Power

4. Section 1 Electric Potential Chapter 17 Objectives • Distinguishbetween electrical potential energy, electric potential, and potential difference. • Solveproblems involving electrical energy and potential difference. • Describethe energy conversions that occur in a battery.

5. Section 1 Electric Potential Chapter 17 Electrical Potential Energy • Electrical potential energy is potential energy associated with a charge due to its position in an electric field. • Electrical potential energy is a component of mechanical energy. ME = KE + PEgrav + PEelastic + PEelectric

6. Section 1 Electric Potential Chapter 17 Electrical Potential Energy, continued • Electrical potential energy can be associated with a charge in a uniform field. • Electrical Potential Energy in a Uniform Electric Field PEelectric = –qEd electrical potential energy = –(charge)  (electric field strength)  (displacement from the reference point in the direction of the field)

7. Section 1 Electric Potential Chapter 17 Electrical Potential Energy

8. Section 1 Electric Potential Chapter 17 Potential Difference • Electric Potentialequals the work that must be performed against electric forces to move a charge from a reference point to the point in question, divided by the charge. • The electric potential associated with a charge is the electric energy divided by the charge:

9. Section 1 Electric Potential Chapter 17 Potential Difference, continued • Potential Difference equals the work that must be performed against electric forces to move a charge between the two points in question, divided by the charge. • Potential difference is a change in electric potential.

10. Section 1 Electric Potential Chapter 17 Potential Difference

11. Section 1 Electric Potential Chapter 17 Potential Difference, continued • The potential difference in a uniform field varies with the displacement from a reference point. • Potential Difference in a Uniform Electric Field ∆V = –Ed potential difference = –(magnitude of the electric field  displacement)

12. Section 1 Electric Potential Chapter 17 Sample Problem Potential Energy and Potential Difference A charge moves a distance of 2.0 cm in the direction of a uniform electric field whose magnitude is 215 N/C.As the charge moves, its electrical potential energy decreases by 6.9  10-19 J. Find the charge on the moving particle. What is the potential difference between the two locations?

13. Section 1 Electric Potential Chapter 17 Sample Problem, continued Potential Energy and Potential Difference Given: ∆PEelectric = –6.9  10–19 J d = 0.020 m E = 215 N/C Unknown: q = ? ∆V = ?

14. Section 1 Electric Potential Chapter 17 Sample Problem, continued Potential Energy and Potential Difference Use the equation for the change in electrical potential energy. PEelectric = –qEd Rearrange to solve for q, and insert values.

15. Section 1 Electric Potential Chapter 17 Sample Problem, continued Potential Energy and Potential Difference The potential difference is the magnitude of E times the displacement.

16. Section 1 Electric Potential Chapter 17 Potential Difference, continued • At right, the electric poten-tial at point A depends on the charge at point B and the distance r. • An electric potential exists at some point in an electric field regardless of whether there is a charge at that point.

17. Section 1 Electric Potential Chapter 17 Potential Difference, continued • The reference point for potential difference near a point charge is often at infinity. • Potential Difference Between a Point at Infinity and a Point Near a Point Charge • The superposition principle can be used to calculate the electric potential for a group of charges.

18. Section 1 Electric Potential Chapter 17 Superposition Principle and Electric Potential

19. Section 2 Capacitance Chapter 17 Objectives • Relatecapacitance to the storage of electrical potential energy in the form of separated charges. • Calculatethe capacitance of various devices. • Calculatethe energy stored in a capacitor.

20. Section 2 Capacitance Chapter 17 Capacitors and Charge Storage • A capacitoris a device that is used to store electrical potential energy. • Capacitance is the ability of a conductor to store energy in the form of electrically separated charges. • The SI units for capacitance is thefarad,F, which equals a coulomb per volt (C/V)

21. Section 2 Capacitance Chapter 17 Capacitors and Charge Storage, continued • Capacitanceis the ratio of charge to potential difference.

22. Section 2 Capacitance Chapter 17 Capacitance

23. Section 2 Capacitance Chapter 17 Capacitors and Charge Storage, continued • Capacitancedepends on the size and shape of a capacitor. • Capacitance for a Parallel-Plate Capacitor in a Vacuum

24. Section 2 Capacitance Chapter 17 Capacitors and Charge Storage, continued • The material between a capacitor’s plates can change its capacitance. • The effect of a dielectric is to reduce the strength of the electric field in a capacitor.

25. Section 2 Capacitance Chapter 17 Capacitors in Keyboards

26. Section 2 Capacitance Chapter 17 Parallel-Plate Capacitor

27. Section 2 Capacitance Chapter 17 Energy and Capacitors • The potential energy stored in a charged capacitor depends on the charge and the potential difference between the capacitor’s two plates.

28. Section 2 Capacitance Chapter 17 Sample Problem Capacitance A capacitor, connected to a 12 V battery, holds 36 µC of charge on each plate. What is the capacitance of the capacitor? How much electrical potential energy is stored in the capacitor? Given: Q = 36 µC = 3.6  10–5 C ∆V = 12 V Unknown: C = ? PEelectric = ?

29. Section 2 Capacitance Chapter 17 Sample Problem, continued Capacitance To determine the capacitance, use the definition of capacitance.

30. Section 2 Capacitance Chapter 17 Sample Problem, continued Capacitance To determine the potential energy, use the alternative form of the equation for the potential energy of a charged capacitor:

31. Section 3 Current and Resistance Chapter 17 Objectives • Describethe basic properties of electric current, and solve problems relating current, charge, and time. • Distinguishbetween the drift speed of a charge carrier and the average speed of the charge carrier between collisions. • Calculateresistance, current, and potential difference by using the definition of resistance. • Distinguishbetween ohmic and non-ohmic materials, and learn what factors affect resistance.

32. Section 3 Current and Resistance Chapter 17 Current and Charge Movement • Electric currentis the rate at which electric charges pass through a given area.

33. Section 3 Current and Resistance Chapter 17 Conventional Current

34. Section 3 Current and Resistance Chapter 17 Drift Velocity • Drift velocityis the the net velocity of a charge carrier moving in an electric field. • Drift speeds are relatively small because of the many collisions that occur when an electron moves through a conductor.

35. Section 3 Current and Resistance Chapter 17 Drift Velocity

36. Section 3 Current and Resistance Chapter 17 Resistance to Current • Resistanceis the opposition presented to electric current by a material or device. • The SI units for resistance is the ohm (Ω) and is equal to one volt per ampere. • Resistance

37. Section 3 Current and Resistance Chapter 17 Resistance to Current, continued • For many materials resistance is constant over a range of potential differences. These materials obey Ohm’s Law and are calledohmic materials. • Ohm’s low does not hold for all materials. Such materials are callednon-ohmic. • Resistance depends on length, cross-sectional area, temperature, and material.

38. Section 3 Current and Resistance Chapter 17 Factors that Affect Resistance

39. Section 3 Current and Resistance Chapter 17 Resistance to Current, continued • Resistors can be used to control the amount of current in a conductor. • Salt water and perspiration lower the body's resistance. • Potentiometershave variable resistance.

40. Section 4 Electric Power Chapter 17 Objectives • Differentiatebetween direct current and alternating current. • Relateelectric power to the rate at which electrical energy is converted to other forms of energy. • Calculateelectric power and the cost of running electrical appliances.

41. Section 4 Electric Power Chapter 17 Sources and Types of Current • Batteries and generators supply energy to charge carriers. • Current can be direct or alternating. • In direct current, charges move in a single direction. • Inalternating current, the direction of charge movement continually alternates.

42. Section 4 Electric Power Chapter 17 Energy Transfer • Electric power is the rate of conversion of electrical energy. • Electric power P = I∆V Electric power = current  potential difference

43. Section 4 Electric Power Chapter 17 Energy Transfer

44. Section 4 Electric Power Chapter 17 Energy Transfer, continued • Power dissipated by a resistor • Electric companies measure energy consumed inkilowatt-hours. • Electrical energy is transferred at high potential differences to minimize energy loss.

45. Section 4 Electric Power Chapter 17 Relating Kilowatt-Hours to Joules

46. Chapter 17 Standardized Test Prep Multiple Choice 1. What changes would take place if the electron moved from point A to point B in the uniform electric field? A. The electron’s electrical potential energy would increase; its electric potential would increase. B. The electron’s electrical potential energy would increase; its electric potential would decrease. C. The electron’s electrical potential energy would decrease; its electric potential would decrease. D. Neither the electron’s electrical potential energy nor its electric potential would change.

47. Chapter 17 Standardized Test Prep Multiple Choice, continued 1. What changes would take place if the electron moved from point A to point B in the uniform electric field? A. The electron’s electrical potential energy would increase; its electric potential would increase. B. The electron’s electrical potential energy would increase; its electric potential would decrease. C. The electron’s electrical potential energy would decrease; its electric potential would decrease. D. Neither the electron’s electrical potential energy nor its electric potential would change.

48. Chapter 17 Standardized Test Prep Multiple Choice, continued 2. What changes would take place if the electron moved from point A to point C in the uniform electric field? F. The electron’s electrical potential energy would increase; its electric potential would increase. G. The electron’s electrical potential energy would increase; its electric potential would decrease. H. The electron’s electrical potential energy would decrease; its electric potential would decrease. J. Neither the electron’s electrical potential energy nor its electric potential would change.

49. Chapter 17 Standardized Test Prep Multiple Choice, continued 2. What changes would take place if the electron moved from point A to point C in the uniform electric field? F. The electron’s electrical potential energy would increase; its electric potential would increase. G. The electron’s electrical potential energy would increase; its electric potential would decrease. H. The electron’s electrical potential energy would decrease; its electric potential would decrease. J. Neither the electron’s electrical potential energy nor its electric potential would change.

50. Chapter 17 Standardized Test Prep Multiple Choice, continued Use the following passage to answer questions 3–4. A proton (q = 1.6  10–19 C) moves 2.0  10–6 m in the direction of an electric field that has a magnitude of 2.0 N/C. 3. What is the change in the electrical potential energy associated with the proton? A. –6.4  10–25 J B. –4.0  10–6 V C. +6.4  10–25 J D. +4.0  10–6 V