Electric Field and the concept of Electromagnetism

Micheal Faraday first introduced the idea of electric fields and electromagnetism. He to coil of copper and attached an Ammeter to it. Then he put a magnet thorough the coil and observed a flow of electricity. The he pulled the magnet out and observed that there was no electricity.

An electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding.


An electric field that changes with time, such as due to the motion of charged particles in the field, influences the local magnetic field. That is, the electric and magnetic fields are not completely separate phenomena; what one observer perceives as an electric field, another observer in a different frame of reference perceives as a mixture of electric and magnetic fields. For this reason, one speaks of electromagnetism or electromagnetic fields.

The electric field intensity is defined as the force per unit positive charge that would be experienced by a stationary point charge, or "test charge", at a given location in the field:

where

F is the electric force experienced by the test particle

q_t is the charge of the test particle in the electric field

E is the electric field wherein the particle is located.

Taken literally, this equation only defines the electric field at a specific location as the force experienced by a stationary test charge at that point (with the sign of q_t, positive or negative, determining the direction of the force). Given that electric fields are generated by electrically charged particles, adding or moving a source charge, q_s, will alter the electric field distribution. Therefore, it is important to remember that an electric field is defined with respect to a particular configuration of source charges. In practice, this is achieved by placing test particles with successively smaller electric charge in the vicinity of the source distribution and measuring the force exerted on the test charges as their charge approaches zero.

This allows the electric field to be determined from the distribution of its source charges alone.

As is clear from the definition, the direction of the electric field is the same as the direction of the force it would exert on a positively-charged particle, and opposite the direction of the force on a negatively-charged particle. Since like charges repel and opposites attract (as quantified below), the electric field tends to point away from positive charges and towards negative charges.

Based on Coulomb's law for interacting point charges, the contribution to the E-field at a point in space due to a single, discrete charge located at another point in space is given by the following:

where

Q is the charge of the particle creating the electric force,

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 electric constant.

The total E-field due to a quantity of point charges, n_q, is simply the superposition of the contribution of each individual point charge:

Alternatively, Gauss's law allows the E-field to be calculated in terms of a continuous distribution of charge density in space, ρ:

Coulomb's law is actually a special case of Gauss's Law, a more fundamental description of the relationship between the distribution of electric charge in space and the resulting electric field. Gauss's law is one of Maxwell's equations, a set of four laws governing electromagnetic.

Electromagnetism: Electromagnetism is the force that causes the interaction between electrically charged particles; the areas in which this happens are called electromagnetic fields. It is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation.

Electromagnetism is the interaction responsible for practically all the phenomena encountered in daily life, with the exception of gravity. Ordinary matter takes its form as a result of intermolecular forces between individual molecules in matter. Electrons are bound by electromagnetic wave mechanics into orbitals around atomic nuclei to form atoms, which are the building blocks of molecules. This governs the processes involved in chemistry, which arise from interactions between the electrons of neighboring atoms, which are in turn determined by the interaction between electromagnetic force and the momentum of the electrons.

Electromagnetism manifests as both electric fields and magnetic fields. Both fields are simply different aspects of electromagnetism, and hence are intrinsically related. Thus, a changing electric field generates a magnetic field; conversely a changing magnetic field generates an electric field. This effect is called electromagnetic induction, and is the basis of operation for electrical generators, induction motors, and transformers. Mathematically speaking, magnetic fields and electric fields are convertible with relative motion as a 2nd-order tensor or bivector.

Electric fields are the cause of several common phenomena, such as electric potential (such as the voltage of a battery) and electric current(such as the flow of electricity through a flashlight). Magnetic fields are the cause of the force associated with magnets.