《Fundamentals of Physics精品教学-华南理工》21 Electric Charge.pptVIP

21-1 Electromagnetism Electrical phenomena → Electricity Magnetic phenomena → Magnetism Electricity produces magnetism Magnetism produces electricity Electricity and magnetism are connected each other → Electromagnetism (1820) This connection is represented in the Maxwell’s law Fundamentals of Physics 21 Electric Charge 21-2 Electric Charge Clothing spark and lightning → indications of vast amount of electric charge Electric charge → an intrinsic characteristic of fundamental particles Two kinds of charges in the nature → +, – Electrically neutral To charge an object Fundamentals of Physics 21 Electric Charge Charges with the same electrical sign repel each other; and charges with opposite electrical signs attract each other Industrial applications Fundamentals of Physics 21 Electric Charge 21-2 Electric Charge Electrostatic separation Photocopying Fundamentals of Physics 21 Electric Charge electrostatic precipitation (dust collection) Fundamentals of Physics 21 Electric Charge Conductor — negative charge can move freely ( metals, tap water, and human body) Insulator — can not move freely (glass, pure water, and plastic) Semiconductor (silicon, germ.) Superconductor Fundamentals of Physics 21 Electric Charge 21-3 Conductors and Insulators Fundamentals of Physics 21 Electric Charge Induced charge The properties of conductors and insulators are due to the structure and electrical nature of atoms 21-3 Conductors and Insulators conduction electrons chlorine kalium 21-4 Coulomb’s law electrostatic force Fundamentals of Physics 21 Electric Charge apply in every realm The SI unit of charge coulomb (C) electrostatic constant permittivity constant Fundamentals of Physics 21 Electric Charge inverse square law 21-4 Coulomb’s law Principle of superposition Fundamentals of Physics 21 Electric Charge 21-4 Coulomb’s law Two shell theorems: (1) A shell of uniform charge attracts or repels a charged particle that i