Electromagnetism FF95594731A UNERDSAMS OFAMERIC F6 FF95594731A oN HoNDiEDDorves
Electromagnetism
Agenda today: Electric charge(电量) Coulomb'sLaw(库仑定律) Electric field(电场)
Agenda today: Electric charge（电量） Coulomb’s Law（库仑定律） Electric field（电场）
Charging by friction Table 8.1 The Electrostatic Series Cat's fur Low affinity Acetate for electrons Glass Wool Lead Silk Wax Ebonite Copper Rubber A plastic comb that has been charged by Amber running it through your hair attracts neutral objects such as bits of paper or, Sulphur High affinity as seen here,drops of water. Gold for electrons
顿牟掇芥 ,磁石 引针 Charging by friction
Charging by induction Spinning Plastic Wheels
Charging by induction
Static electricity(静电学) The property of electric charge: 1.There are two kinds of electric charge,positive charge and negative charge. 2.Like charges repel.And unlike charge attract. 3.Free charge is quantified in positive or negative integral multiples of e. e=1.602*10-19C
Static electricity(静电学） The property of electric charge: 1. There are two kinds of electric charge, positive charge and negative charge. 2. Like charges repel. And unlike charge attract. 3. Free charge is quantified in positive or negative integral multiples of e. e=1.602*10-19 C
Fig.8.49 Millikan's oil-drop apparatus Fig.8.50 Millikan used a horizontally oriented parallel-plate capacitor to create the electric force because of its uniform electric field and the ease of controlling and calculating the electric field strength
The conservation law of electric charge The net charge is the same before and after any interaction
The conservation law of electric charge The net charge is the same before and after any interaction
Coulomb's law F匹& Where 8o is the permittivity(介电系数，电容率)of free space
Coulomb’s law Where 0 is the permittivity（介电系数，电容率） of free space
The application of static electric force:electrostatic copier Surface of drum Toner particles held to drum surface FIGURE 16-41 Problem 52
The application of static electric force: electrostatic copier