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Chương 1 Từ trường PHYSICS 1 MECHANICSAND THERMODYNAMICS PHYSICS 2 ELECTRICITY, MAGNETISM, OPTICS, AND MODERN PHYSICS PART 4 Electricity and Magnetism Chapter 1 Electric Fields Chapter 2 Gauss’s Law Chapter 3 Electric Potential Chapter 4 Capacitance and Dielectrics Chapter 5 Current and Resistance Chapter 6 Direct Current Circuits Chapter 7 Magnetic Fields Chapter 8 Sources of the Magnetic Field Chapter 9 Faraday’s Law CHAPTER 1 (3) ELECTRIC FIELDS 1 1 Properties of Electric Charges 1 2 Charging.
PHYSICS 1: MECHANICS AND THERMODYNAMICS PHYSICS 2: ELECTRICITY, MAGNETISM, OPTICS, AND MODERN PHYSICS PART Electricity and Magnetism Chapter 1: Electric Fields Chapter 2: Gauss’s Law Chapter 3: Electric Potential Chapter 4: Capacitance and Dielectrics Chapter 5: Current and Resistance Chapter 6: Direct-Current Circuits Chapter 7: Magnetic Fields Chapter 8: Sources of the Magnetic Field Chapter 9: Faraday’s Law CHAPTER ELECTRIC FIELDS 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Properties of Electric Charges Charging Objects by Induction Coulomb’s Law Analysis Model: Particle in a Field (Electric) Electric Field of a Continuous Charge Distribution Electric Field Lines (study in chapter 2) Motion of a Charged Particle in a Uniform Electric Field (3) CHAPTER - ELECTRIC FIELDS 1.1 Properties of Electric Charges Two types of charges: positive and negative Charge interaction: Charge of the same sign repel one another Charges with opposite signs attract one another Electric charge is always conserved in an isolated system CHAPTER - ELECTRIC FIELDS 1.1 Properties of Electric Charges Electric charge always occurs as integral multiples of a fundamental amount of charge 𝑒 (quantized): 𝑞 = ±𝑁𝑒 Neutron: 𝑞𝑛 = 0, Proton: 𝑞𝑝 = 𝑒, Electron: 𝑞𝑒 = −𝑒 Positive ion: 𝑞+ = 𝑁𝑒, Negative ion: 𝑞− = −𝑁𝑒 CHAPTER - ELECTRIC FIELDS 1.1 Properties of Electric Charges Three objects are brought close to each other, two at a time When objects A and B are brought together, they repel When objects B and C are brought together, they also repel Which of the following are true? (a) Objects A and C possess charges of the same sign (b) Objects A and C possess charges of opposite sign (c) All three objects possess charges of the same sign (d) One object is neutral (e) Additional experiments must be performed to determine the signs of the charges CHAPTER - ELECTRIC FIELDS 1.2 Charging Objects by Induction Electrical conductors are materials in which some of the electrons are free electrons that are not bound to atoms and can move relatively freely through the material Ex.: copper, aluminum, silver,… Electrical insulators are materials in which all electrons are bound to atoms and cannot move freely through the material Ex.: glass, rubber, dry wood,… Semiconductors are a third class of materials, and their electrical properties are somewhere between those of insulators and those of conductors Ex.: Silicon, germanium,… CHAPTER - ELECTRIC FIELDS 1.2 Charging Objects by Induction CHAPTER - ELECTRIC FIELDS 1.2 Charging Objects by Induction Three objects are brought close to one another, two at a time When objects A and B are brought together, they attract When objects B and C are brought together, they repel Which of the following are necessarily true? (a) Objects A and C possess charges of the same sign (b) Objects A and C possess charges of opposite sign (c) All three objects possess charges of the same sign (d) One object is neutral (e) Additional experiments must be performed to determine information about the charges on the objects 1.3 Coulomb’s Law CHAPTER - ELECTRIC FIELDS Electric force between two stationary point charges (called electrostatic force or Coulomb force): 𝒒𝟏 𝒒𝟐 𝑭 𝒆 = 𝒌𝒆 𝒓𝟐 Coulomb constance: 𝑘𝑒 = = 8.987 × 109 N m2 /C 4𝜋𝜀0 where 𝜀0 is permittivity of free space 𝜀0 = 8.854 × 10−12 C /m2 N 𝑞1 , 𝑞2 : magnitude of point charges 𝑟: distance between two charges Point charge: charged particle of zero size ...