Chapter 19 lectric Charge and Electric Field Description (1)It is an exp Law, holds both for macroscopic microscopic, only holds for "point charge" model. (2) There are four basic physical quantities for electromagnetic quantity in the sI system. They are length(m), mass(kg), time(s), current(a). 3)principle of superposition p462. The net force on any one of them will be the vector sum of the forces due to each of the others Ⅴ ector 1=∑ i1 i SuIn
Chapter 19 Electric Charge and Electric Field (1) It is an exp. Law, holds both for macroscopic & microscopic, only holds for “point charge” model. (2) There are four basic physical quantities for electromagnetic quantity in the SI system. They are length (m), mass(kg), time(s), current(A). (3) principle of superposition p462. The net force on any one of them will be the vector sum of the forces due to each of the others. = i F1 Fi1 Vector sum Description:
Chapter 19 Electric Charge and Electric Field Example (p462): The electron and proton of a hydrogen atom are separated (on the average) by a distance of about 5.3x10-l m. Find the magnitude of the electric force that each particle exerts on the other Solution:q1=-1.60x10-19C,q2=1.60x109C, r=5.3x10lm From coulomb’slaw F=k=8990×1.6×0y =8.2×10-8N 5.3×10
Chapter 19 Electric Charge and Electric Field Example (p462): The electron and proton of a hydrogen atom are separated (on the average) by a distance of about 5.3x10-11 m. Find the magnitude of the electric force that each particle exerts on the other. q1 =-1.60x10-19 C, q2 =1.60x10-19 C, r = 5.3x10-11 m ( ) ( ) 2 2 2 2 19 9 8 2 2 11 1.6 10 8.99 10 8.2 10 5.3 10 Nm e e C e C F k N r m − − − = = = From Coulomb’s law Solution:
Chapter 19 Electric Charge and Electric Field 例:经典的氢原子中电子绕核旋转,质子质量MD= 167×1027kg,电子质量m2=9.11×1031kg,求电子 与质子间的库仑力F与万有引力F之比。 解:库仑力大小 F 1q1 1 e aTE ,24兀80 万有引力大小 Gm12=G pe F1 e Fu 4IGoG m, me =226×1039 (微观领域中,万有引力比库仑力小得多,可忽略不计
Chapter 19 Electric Charge and Electric Field 例：经典的氢原子中电子绕核旋转，质子质量 Mp = 1.6710-27 kg , 电子质量 me= 9.1110-31 kg , 求电子 与质子间的库仑力Fe与万有引力F引之比。 解：库仑力大小 2 1 2 4 0 1 r q q Fe = 2 2 4 0 1 r e = 万有引力大小 2 1 2 r m m F引 = G 2 r m m G p e = p e e m m e F G F 2 4 0 1 = 引 39 = 2.2610 （微观领域中,万有引力比库仑力小得多,可忽略不计.）
Chapter 19 Electric Charge and Electric Field 19-6819-7819-11 Electric Field(静电场) (p464-471,476-477) Coulomb's interaction is at a distance how does q1“know” of the presence of q2? How the force of q1 acts on the point charge q2? 实验证实了两静止电荷间存在相互作用的静电力, 但其相互作用是怎样实现的? 电场 电荷一 电荷 场是一种特殊形态的物质 场 物质 实物
Chapter 19 Electric Charge and Electric Field 19-6&19-7&19-11 Electric Field (静电场) (p464-471,476-477) Coulomb’s interaction is at a distance. How does q1 “know” of the presence of q2? How the force of q1 acts on the point charge q2? 实验证实了两静止电荷间存在相互作用的静电力， 但其相互作用是怎样实现的？ 电 荷 电 场 电 荷 场是一种特殊形态的物质 实物 物 质 场
Chapter 19 Electric Charge and Electric Field 1. The Electric Field(P464): In the 19th century, British experimental physicist Michael faraday proposed the electric field Charge q,- Electric Field 1= Charge q Electric field 2 vectorfield It is similar to gravitational field 2. The basic feature of electric field Giving an acting force to any charge init(对放其内的任何电荷都有作用力)→E The electric force does work on moving charge(电场力对移动电荷作功)-;
Chapter 19 Electric Charge and Electric Field In the 19th century, British experimental physicist Michael Faraday proposed the electric field Charge q1 Electric Field 1 Electric Field 2 Charge q2 1. The Electric Field (P464): vector field It is similar to gravitational field！ 2. The Basic Feature of Electric Field Giving an acting force to any charge in it (对放其内的任何电荷都有作用力) ; E The electric force does work on moving charge (电场力对移动电荷作功) V ;