Здавалка
Главная | Обратная связь

Energy of electric field.



The electrostatic field stores energy. The energy density u (energy per unit volume) is given by[2]

where ε is the permittivity of the medium in which the field exists, and E is the electric field vector.

The total energy U stored in the electric field in a given volume V is therefore

 

Potential, potential difference.

Voltage, otherwise known as electrical potential difference or electric tension (denoted ∆V and measured in units of electric potential: volts, or joules per coulomb), is the electric potential difference between two points — or the difference in electric potential energy of a unit test charge transported between two points.[1] Voltage is equal to the work which would have to be done, per unit charge, against a static electric field to move the charge between two points. A voltage may represent either a source of energy (electromotive force), or it may represent lost, used, or stored energy (potential drop). A voltmeter can be used to measure the voltage (or potential difference) between two points in a system; usually a common reference potential such as the ground of the system is used as one of the points. Voltage can be caused by static electric fields, by electric current through a magnetic field, by time-varying magnetic fields, or a combination of all three.

Work in electrostatic field.

Electrical work is the work done on a charged particle by an electric field. The equation for 'electrical' work is, naturally, equivalent to that of 'mechanical' work:

where

Q is the charge of the particle, q, the unit charge

E is the electric field, which at a location is the force at that location divided by a unit ('test') charge

FE is the Coulomb (electric) force

r is the displacement

is the dot product

Joule law.

Joule’s law, in electricity, mathematical description of the rate at which resistance in a circuit converts electric energy into heat energy. The English physicist James Prescott Joule discovered in 1840 that the amount of heat per second that develops in a wire carrying a current is proportional to the electrical resistance of the wire and the square of the current. He determined that the heat evolved per second is equivalent to the electric power absorbed, or the power loss.

A quantitative form of Joule’s law is that the heat evolved per second, or the electric power loss, P,equals the current I squared times the resistance R, or P = I2R. The power P has units of watts, or joules per second, when the current is expressed in amperes and the resistance in ohms.







©2015 arhivinfo.ru Все права принадлежат авторам размещенных материалов.