2004/12/30 | 库仑力[Coulomb Force]
类别(Ω〖物理〗) | 评论(1) | 阅读(158) | 发表于 17:44
The Coulomb force between two or more charged bodies is the force between them due to Coulomb's law. If the particles are both positively or negatively charged, the force is repulsive; if they are of opposite charge, it is attractive.
By the middle of eighteenth century, only the qualitative aspects of the electric force were known. Scientists started to speculate about the quantitative aspect of the force and the idea that the electric force could be similarly to the gravitational force, i.e., proportional to the inverse of the square of the distance. In 1777-1785, Charles Augustine Coulomb proved experimentally that indeed the electric force was proportional to the inverse of the square of the distance. Coulomb stated that the force that acts in two electrically charged bodies is proportional to the product of the module of their charges divided by the square of the distance d between them,
(1)

This called Coulomb's law and was the first attempt to understand the electric force.
Like the gravitational force, the Coulomb force is an inverse square law. Unlike the gravitational force however, the Coulomb (or electric) force may be either attractive or repulsive, depending on the signs of the charges and .
The Coulomb force F on a charged particle due to another charge can be obtained by multiplying the electric field caused by by the charge . The constant of proportionality in (1) depends on the choice of units used. In the MKS system of units, the constant of proportionality is called Coulomb's constant.
In a vacuum,
(2)

in cgs, and
(3)

in MKS, where is the permittivity of free space, and
(4)

is Coulomb's constant, with the positions of the particles being r and , respectively.
The magnitude of the force is then given by
(5)

in cgs, and
(6)

in MKS, where is the distance between the two particles.
The development of the full theory of electromagnetism showed that the force that acts on a particular charge--no matter how many other charges there are or how they are moving--depends only on the position of that particular charge, on the velocity of the charge, and on the amount of charge. In fact, the electromagnetic force F on a charge q moving with a velocity v (known as the Lorentz force) can be written as
(7)

where E is the electric field and B the magnetic field at the position of the charge.
0

评论Comments

日志分类
首页[1408]
∑〖数学〗[349]
Ω〖物理〗[357]
¤〖天文〗[343]
℃〖化学〗[359]