The region of electric influence surrounding positive or negative electric charges; symbol E, units V/m (volts per metre); a vector quantity, with field direction specified as the direction of motion of a positive charge placed in the field. For a force F on a test charge of q coulombs, the field is given as E = F/q, ie the electric field is the electric force per unit charge. It may be represented using field lines.
(Discuss)| Electromagnetism | |
| Magnetism | |
| Electrostatics | |
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| Electric charge | |
| Coulomb's law | |
| Electric field | |
| Gauss's law | |
| Electric potential | |
| Magnetostatics | |
| Ampere's law | |
| Magnetic field | |
| Magnetic moment | |
| Electrodynamics | |
| Electric current | |
| Lorentz force law | |
| Electromotive force | |
| Electromagnetic induction | |
| Faraday-Lenz law | |
| Displacement current | |
| Maxwell's equations | |
| Electromagnetic field | |
| Electromagnetic radiation | |
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| Electrical resistance | |
| Capacitance | |
| Inductance | |
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In physics, the space surrounding an electric charge has a property called an electric field.
A moving charge creates not just an electric field but also a magnetic field, and in general the electric and magnetic fields are not completely separate phenomena;
The electric field is defined as the proportionality constant between charge and force (in other words, the force per unit of test charge):
where
is the electric force given by Coulomb's law, q is the charge of a "test charge",However, note that this equation is only true in the case of electrostatics, that is to say, when there is nothing moving.
Coulomb's law
The field surrounding a point charge is given by Coulomb's law:
where
Q is the charge of the particle creating the electric field, r is the distance from the particle with charge Q to the E-field evaluation point, is the Unit vector pointing from the particle with charge Q to the E-field evaluation point, ε0 is the Permittivity of free space. If more than one charge is present, the total electric field at any point is equal to the vector sum of the respective electric fields that each object would create in the absence of the others.Considering the permittivity of a material, which may differ from the permittivity of free space , the electric displacement field is:
Energy in the electric field
The electric field stores energy. The energy density of the electric field is given by
where
ε is the permittivity of the medium in which the field exists, E is the electric field vector.Parallels between electrostatics and gravity
Coulomb's law, which describes the interaction of electric charges:
is similar to the Newtonian gravitation law:
This suggests similarities between the electric field E and the gravitational field g, so sometimes mass is called "gravitational charge". As they move, they generate magnetic fields, and if the magnetic field changes, it generates electric fields. This "secondary" electric field can be computed using Faraday's law of induction,
where
indicates the curl of the electric field, represents the vector rate of decrease of magnetic flux density with time.
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