Electromagnetic fields

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Patients in hospitals can be exposed to electromagnetic fields and optical radiation. Electromagnetic fields are omnipresent in daily life. They can arise as a by-product of the generation, transport and use of electricity. Nederlands English. RIVM Committed to health and sustainability. Home Electromagnetic Fields Electromagnetic Fields. Electromagnetic fields arise, among others, with the generation, transport or use of electricity and wireless communication.

If the fields are strong enough, health risks may occur. The fields can be stronger at work and in hospitals than in daily life. Go to next slide: Active slide:. More details about the main research topics on EMF within RIVM National Institute for Public Health and the Environment can be found on the following webpages: Electromagnetic fields in daily life Electromagnetic fields at work Electromagnetic fields and optical radiation in hospitals. Page Publications Related subjects.

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Electromagnetic fields in daily life In daily life everybody is, to a greater or lesser degree, exposed to electromagnetic fie. Electromagnetic fields and optical radiation in hospitals Patients in hospitals can be exposed to electromagnetic fields and optical radiation. National precautionary policies on magnetic fields from power lines in Belgium, France, Germany, the Netherlands and the United Kingdom.

Possible solutions. Onderzoek naar mogelijke langetermijneffecten van elektromagnetische velden op de gezondheid van werknemers. Electromagnetic fields in the working environment. Elektromagnetische velden in arbeidssituaties.

Physical Science 6.8a - Electric Current and Magnetic Fields

Dosisbesparing bij radiologische apparatuur. Recent developments in medical techniques involving ionising or non-ionising radiation : Update However, if either the electric or magnetic field has a time-dependence, then both fields must be considered together as a coupled electromagnetic field using Maxwell's equations. With the advent of special relativity , physical laws became susceptible to the formalism of tensors. Maxwell's equations can be written in tensor form, generally viewed by physicists as a more elegant means of expressing physical laws.

The behaviour of electric and magnetic fields, whether in cases of electrostatics, magnetostatics, or electrodynamics electromagnetic fields , is governed by Maxwell's equations. In the vector field formalism, these are:. The units used above are the standard SI units. Inside a linear material, Maxwell's equations change by switching the permeability and permittivity of free space with the permeability and permittivity of the linear material in question. Inside other materials which possess more complex responses to electromagnetic fields, these terms are often represented by complex numbers, or tensors.

The Lorentz force law governs the interaction of the electromagnetic field with charged matter. When a field travels across to different media, the properties of the field change according to the various boundary conditions. These equations are derived from Maxwell's equations. The tangential components of the electric and magnetic fields as they relate on the boundary of two media are as follows: [11].

Faraday's Law may be stated roughly as 'a changing magnetic field creates an electric field'. This is the principle behind the electric generator. Ampere's Law roughly states that 'a changing electric field creates a magnetic field'. Thus, this law can be applied to generate a magnetic field and run an electric motor. Under these conditions, the electric and magnetic fields satisfy the electromagnetic wave equation : [12]. James Clerk Maxwell was the first to obtain this relationship by his completion of Maxwell's equations with the addition of a displacement current term to Ampere's circuital law.

Being one of the four fundamental forces of nature, it is useful to compare the electromagnetic field with the gravitational , strong and weak fields.

Electromagnetic Fields: MedlinePlus

The word 'force' is sometimes replaced by 'interaction' because modern particle physics models electromagnetism as an exchange of particles known as gauge bosons. Sources of electromagnetic fields consist of two types of charge — positive and negative. This contrasts with the sources of the gravitational field, which are masses. Masses are sometimes described as gravitational charges , the important feature of them being that there are only positive masses and no negative masses.

Further, gravity differs from electromagnetism in that positive masses attract other positive masses whereas same charges in electromagnetism repel each other. The relative strengths and ranges of the four interactions and other information are tabulated below:. When an EM field see electromagnetic tensor is not varying in time, it may be seen as a purely electrical field or a purely magnetic field, or a mixture of both.

However the general case of a static EM field with both electric and magnetic components present, is the case that appears to most observers. Observers who see only an electric or magnetic field component of a static EM field, have the other electric or magnetic component suppressed, due to the special case of the immobile state of the charges that produce the EM field in that case.

What are electromagnetic fields?

In such cases the other component becomes manifest in other observer frames. That is, a pure static electric field will show the familiar magnetic field associated with a current, in any frame of reference where the charge moves. Likewise, any new motion of a charge in a region that seemed previously to contain only a magnetic field, will show that the space now contains an electric field as well, which will be found to produces an additional Lorentz force upon the moving charge.

Thus, electrostatics , as well as magnetism and magnetostatics , are now seen as studies of the static EM field when a particular frame has been selected to suppress the other type of field, and since an EM field with both electric and magnetic will appear in any other frame, these "simpler" effects are merely the observer's. The "applications" of all such non-time varying static fields are discussed in the main articles linked in this section.

An electromagnetic field very far from currents and charges sources is called electromagnetic radiation EMR since it radiates from the charges and currents in the source, and has no "feedback" effect on them, and is also not affected directly by them in the present time rather, it is indirectly produced by a sequences of changes in fields radiating out from them in the past. EMR consists of the radiations in the electromagnetic spectrum , including radio waves , microwave , infrared , visible light , ultraviolet light , X-rays , and gamma rays.

The many commercial applications of these radiations are discussed in the named and linked articles. A notable application of visible light is that this type of energy from the Sun powers all life on Earth that either makes or uses oxygen.

Safety of 5G Mobile Networks

This type of dipole field near sources is called an electromagnetic near-field. Changing electric dipole fields, as such, are used commercially as near-fields mainly as a source of dielectric heating. Otherwise, they appear parasitically around conductors which absorb EMR, and around antennas which have the purpose of generating EMR at greater distances. Changing magnetic dipole fields i. These include motors and electrical transformers at low frequencies, and devices such as metal detectors and MRI scanner coils at higher frequencies.

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Sometimes these high-frequency magnetic fields change at radio frequencies without being far-field waves and thus radio waves; see RFID tags. See also near-field communication. Further uses of near-field EM effects commercially, may be found in the article on virtual photons , since at the quantum level, these fields are represented by these particles. Far-field effects EMR in the quantum picture of radiation, are represented by ordinary photons.

The potential effects of electromagnetic fields on human health vary widely depending on the frequency and intensity of the fields. The potential health effects of the very low frequency EMFs surrounding power lines and electrical devices are the subject of on-going research and a significant amount of public debate.

Electromagnetic field

NIOSH has issued some cautionary advisories but stresses that the data are currently too limited to draw good conclusions. On the other hand, radiation from other parts of the electromagnetic spectrum , such as ultraviolet light and gamma rays , are known to cause significant harm in some circumstances.

For more information on the health effects due to specific electromagnetic phenomena and parts of the electromagnetic spectrum , see the following articles:. From Wikipedia, the free encyclopedia.

Electric and magnetic fields produced by moving charged objects. For the British hacker convention, see Electromagnetic Field festival. Electrical network.

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Covariant formulation. Electromagnetic tensor stress—energy tensor. Main article: Mathematical descriptions of the electromagnetic field. Main article: Fundamental forces.

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This section needs expansion. You can help by adding to it. June Main articles: electrostatics , magnetostatics , and magnetism. Main articles: near and far field , near field optics , virtual particle , dielectric heating , and Electromagnetic induction.

Afterglow plasma Antenna factor Classification of electromagnetic fields Electric field Electromagnetism Electromagnetic propagation Electromagnetic tensor Electromagnetic therapy Free space Fundamental interaction Electromagnetic radiation Electromagnetic spectrum Electromagnetic field measurements Gravitational field List of environment topics Magnetic field Maxwell's equations Photoelectric effect Photon Quantization of the electromagnetic field Quantum electrodynamics Riemann—Silberstein vector SI units.

Addison Wesley Longman. Introduction to Electrodynamics. Chemistry: Structure and Dynamics.