Electric

In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. This electric field exerts a force on other electrically charged objects. The concept of electric field was introduced by Michael Faraday. more...

Home
Bath & Body
Dietary Supplements,...
Hair Care
Hair Removal
Health Care
Makeup
Massage
Medical, Special Needs
Bathroom Safety
Braces, Supports
Hearing Assistance
Incontinence Aids
Mobility Equipment
Lifts
Other
Ramps
Scooters
Walkers & Canes
Wheelchairs
Electric
Manual
Other
Monitoring, Testing
Orthotics, Insoles
Other
Positioning Equipment
Respiratory Aids
Nail
Natural Therapies
Oral Care
Skin Care
Vision Care

The electric field is a vector field with SI units of newtons per coulomb (N C⁻¹) or, equivalently, volts per meter (V m⁻¹). The direction of the field at a point is defined by the direction of the electric force exerted on a positive test charge placed at that point. The strength of the field is defined by the ratio of the electric force on a charge at a point to the magnitude of the charge placed at that point. Electric fields contain electrical energy with energy density proportional to the square of the field intensity. The electric field is to charge as gravitational acceleration is to mass and force density is to volume.

A moving charge has not just an electric field but also a magnetic field, and in general 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.\" In quantum mechanics, disturbances in the electromagnetic fields are called photons, and the energy of photons is quantized.

Definition

A stationary charged particle in an electric field experiences a force proportional to its charge. The electric field is defined as the proportionality constant between charge and force in this relationship:

where electric force on the particle, q is its charge, and

Note that this relationship only holds when the charge is stationary; otherwise the force is determined by the more general Lorentz force equation.

Taken literally, this equation only defines the electric field at the places where there are stationary charges present to experience it. For this reason, physicists use the concept of a test charge: to measure the electric field at a point, you hold a small \"test charge\" there, measure the force, and compute the electric field using the above equation.

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.

Read more at Wikipedia.org