1 / 46

Understanding Electric Potential and Potential Difference

Learn about electrical potential energy, electric potential, and potential difference. Solve problems involving electrical energy and potential difference. Understand the energy conversions in a battery.

lever
Download Presentation

Understanding Electric Potential and Potential Difference

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 17 Section 1 Electric Potential Preview • Objectives • Electrical Potential Energy • Potential Difference • Sample Problem

  2. Chapter 17 Section 1 Electric Potential 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.

  3. Chapter 17 Section 1 Electric Potential 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

  4. Chapter 17 Section 1 Electric Potential 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)

  5. Chapter 17 Section 1 Electric Potential Electrical Potential Energy Click below to watch the Visual Concept. Visual Concept

  6. Chapter 17 Section 1 Electric Potential 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:

  7. Chapter 17 Section 1 Electric Potential 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.

  8. Chapter 17 Section 1 Electric Potential Potential Difference Click below to watch the Visual Concept. Visual Concept

  9. Chapter 17 Section 1 Electric Potential 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)

  10. Chapter 17 Section 1 Electric Potential 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. Chapter 17 Section 1 Electric Potential 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. Chapter 17 Section 1 Electric Potential 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.

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

  14. Chapter 17 Section 1 Electric Potential 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.

  15. Chapter 17 Section 1 Electric Potential 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.

  16. Chapter 17 Section 1 Electric Potential Superposition Principle and Electric Potential Click below to watch the Visual Concept. Visual Concept

  17. Chapter 17 Section 2 Capacitance Preview • Objectives • Capacitors and Charge Storage • Energy and Capacitors • Sample Problem

  18. Chapter 17 Section 2 Capacitance 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.

  19. Chapter 17 Section 2 Capacitance 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)

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

  21. Chapter 17 Section 2 Capacitance Capacitance Click below to watch the Visual Concept. Visual Concept

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

  23. Chapter 17 Section 2 Capacitance 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.

  24. Chapter 17 Section 2 Capacitance Capacitors in Keyboards

  25. Chapter 17 Section 2 Capacitance Parallel-Plate Capacitor Click below to watch the Visual Concept. Visual Concept

  26. Chapter 17 Section 2 Capacitance 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.

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

  29. Chapter 17 Section 2 Capacitance 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 Preview • Objectives • Current and Charge Movement • Drift Velocity • Resistance to Current

  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 Click below to watch the Visual Concept. Visual Concept

  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 Click below to watch the Visual Concept. Visual Concept

  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 Click below to watch the Visual Concept. Visual Concept

  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. Chapter 17 Section 4 Electric Power Preview • Objectives • Sources and Types of Current • Energy Transfer

  41. Chapter 17 Section 4 Electric Power 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.

  42. Chapter 17 Section 4 Electric Power 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.

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

  44. Chapter 17 Section 4 Electric Power Energy Transfer Click below to watch the Visual Concept. Visual Concept

  45. Chapter 17 Section 4 Electric Power 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.

  46. Chapter 17 Section 4 Electric Power Relating Kilowatt-Hours to Joules Click below to watch the Visual Concept. Visual Concept

More Related