Electromagnetism 2004 Fall Zhang Yang Dept. Astron. appl. phys Reference K Electromagnetism, principles and application》 by plorrain d Corson
Electromagnetism 2004 Fall Zhang Yang Dept. Astron. & Appl. Phys Reference: 《 Electromagnetism, principles and application》, by P.Lorrain & D.Corson
Chapter 2 Fields of Stationary Electric Charges Coulombs Law Electric Field intensity E Superposition and Extented Charge Distribution Electric Potential Electric dipole
Chapter 2 Fields of Stationary Electric Charges ◼ Coulomb’s Law ◼ Electric Field Intensity E ◼ Superposition and Extented Charge Distribution ◼ Electric Potential ◼ Electric Dipole
2 1 Coulomb's law Given two stationary point charges @a and Qb, it is experimentally found that the force exerted by a on 1 aqb ab r 丌∈0 where ri is a unIt vector pointing in the direction trom Qa to Qb, and the permittivity of free space(vacuum) 0=8.85187817×10-12 farad/ meter Interpretation
Q Figure 2-1 Charges 2, and 2, separated by a distance r. The force exerted on go by 2 is Fe and is in the direction of r, along the line joining the two charges
Explanation (1) the force acts along the line joining the two charges, in the direction r1 (2 the force is o the product QaQb, so the force is repulsive if Qa & qb are of the same sign attractive if Qa&@b are of the different sign (3 the force x r important.(what if not Unit:(in SI Unit System Fab-- newton; a Abcoulomb; r-meter