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Objectives

Learn about electrical potential energy, potential difference, and capacitance in this comprehensive guide. Explore energy conversions in batteries, solve problems, and calculate charge and potential difference.

michelleanderson
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Objectives

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  1. Section 1 Electric Potential Chapter 17 Objectives • Distinguish between electrical potential energy, electric potential, and potential difference. • Solve problems involving electrical energy and potential difference. • Describe the energy conversions that occur in a battery.

  2. Section 1 Electric Potential Chapter 17 Electrical Potential Energy • Electrical potential energy -energy associated with a charge due to its position in an electric field. • Magnitude of charge in field plays a role! ME = KE + PEgrav + PEelastic + PEelectric

  3. Section 1 Electric Potential Chapter 17 Electrical Potential Energy, continued • Electrical Potential Energy in a Uniform Electric Field PEelectric = –qEd PE =electrical potential energy q=charge E=electric field strength d=distance - PE increases in – charge and decreases if + charge

  4. PE Charge and Direction

  5. Section 1 Electric Potential Chapter 17 Electrical Potential Energy

  6. Section 1 Electric Potential Chapter 17 Potential Difference • Electric Potential= work done against electric force to move a test charge a distance in an electric field. • V=volts= J/C

  7. Section 1 Electric Potential Chapter 17 • Potential difference is a change in electric potential.

  8. Section 1 Electric Potential Chapter 17 Potential Difference

  9. Electric Potential Chapter 17 The potential difference in a uniform field varies with distance from a reference point. • Test charge quantity is irrelevant! • Related to field strength only • Potential Difference in a Uniform Electric Field ∆V = –Ed ∆V=potential difference E=magnitude of the electric field d=displacement

  10. 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?

  11. 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 = ?

  12. Section 1 Electric Potential Chapter 17 Sample Problem, continued Potential Energy and Potential Difference PEelectric = –qEd

  13. Section 1 Electric Potential Chapter 17 Sample Problem, continued Potential Energy and Potential Difference

  14. Section 1 Electric Potential Chapter 17 Potential Difference, continued • At right, the electric potential 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.

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

  16. Section 1 Electric Potential Chapter 17 • reference point for potential difference is infinity. • Equation is

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

  18. Section 2 Capacitance Chapter 17 ` • A capacitor stores electrical potential energy. • units for capacitance is the farad, F = (C/V)

  19. Section 2 Capacitance Chapter 17 Capacitors and Charge Storage, continued Capacitance= charge/volts

  20. Section 2 Capacitance Chapter 17 Capacitance

  21. Section 2 Capacitance Chapter 17 Capacitance for a Parallel-Plate Capacitor in a Vacuum • Capacitancedepends on size and material of a capacitor. • Ε=permitivity constant 8.85X10-12C2/N*m • D= distance • A=area

  22. Section 2 Capacitance Chapter 17 Capacitors and Charge Storage • The material between a capacitor’s plates can change its capacitance. • Computer chips in essence act as 1 E6th tiny capacitors

  23. Section 2 Capacitance Chapter 17 Parallel-Plate Capacitor

  24. Section 2 Capacitance Chapter 17 Energy and Capacitors • The potential energy stored in a charged capacitordepends on the charge and the potential difference between the capacitor’s two plates. • PE=1/2CV2

  25. Honors • C= ε̧ A/d • Where ε = permitivity (from table) • A=area • D=distance of plates

  26. Summing up equations

  27. 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 = ?

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

  29. 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:

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

  31. Section 3 Current and Resistance Chapter 17 Current and Charge Movement • Electric current =rate at which electric charges pass through a circuit. • I=current measured in amperes or (amps) given area.

  32. Section 3 Current and Resistance Chapter 17 Conventional Current

  33. Section 3 Current and Resistance Chapter 17 Drift Velocity • Drift velocity is the the net velocity of a charge in an electric field. • Drift speeds are small

  34. Section 3 Current and Resistance Chapter 17 Ohm’s Law • Resistance =opposition =to electric current . • units =ohm (Ω) volt / ampere. • R=Resistance • V=volts

  35. Section 3 Current and Resistance Chapter 17 Resistance to Current • Ohmic materials=resistance is constant over a range of voltage. • not true for all materials. • Resistance depends on • length, • cross-sectional area, • temperature, and material.

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

  37. Section 3 Current and Resistance Chapter 17 Resistance to Current • Resistorscan be used to control the amount of current in a conductor. • Potentiometers (rheostats, variable resistors) have variable resistance.

  38. 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. • In alternating current, the direction of charge movement continually alternates.

  39. Section 4 Electric Power Chapter 17 Energy Transfer • Electric power is the rate of conversion of electrical energy. • Electric companies measure energy consumed in kilowatt-hours. A kilowatt hour is equal to 3600000 J. • Electrical energy is transferred at high voltage to minimize energy loss. Reduce current increase pressure.

  40. Section 4 Electric Power Chapter 17 Energy Transfer

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

  42. 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.

  43. 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.

  44. 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.

  45. 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.

  46. 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

  47. 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

  48. 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. 4. What is the potential difference between the proton’s starting point and ending point? F. –6.4  10–25 J G. –4.0  10–6 V H. +6.4  10–25 J J. +4.0  10–6 V

  49. 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. 4. What is the potential difference between the proton’s starting point and ending point? F. –6.4  10–25 J G. –4.0  10–6 V H. +6.4  10–25 J J. +4.0  10–6 V

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