Electromagnetic field. Combination of invisible electric and magnetic force fields. Electric fields originate from voltage differences: the higher the voltage, the stronger the resulting field.
[ hide ]
- 1 Magnetic fields
- 2 electromagnetic waves
- 3 Source of magnetic fields
- 1 Classification
- 4 Biological effects and health effects
- 5 Sources
Magnetic fields originate from electric currents: a stronger current results in a stronger field. An electric field exists even if there is no current. When there is current, the magnitude of the magnetic field will change with power consumption, but the strength of the electric field will remain the same.
The movement of electrical charges in a conductive metal (such as a radio or TV station antenna ) causes waves of electric and magnetic fields (called EM electromagnetic waves) that propagate through empty space at the speed c of light. (c = 300,000 km / s). These radiated waves are associated with electromagnetic energy that can be captured by a receiving antenna (the TV antenna in a house or by the small antenna built into a mobile phone).
However, electric and magnetic fields can exist independently of each other, and are then called static fields ; like electric fields that originate between clouds and ground during a storm, before lightning strikes . When electromagnetic energy exists in a region of space, an electromagnetic field is said to exist in that region of space and this field is described in terms of electric field strength (E) and / or magnetic induction or magnetic flux density .
Source of magnetic fields
The source of the magnetic fields is the electric current. Its intensity is measured in amps per meter (A / m). Typically, EMC researchers use a related quantity, flux density (in microtesla (µT) or millitesla (mT). Magnetic fields originate when an electrical device is turned on and current flows. The field strength decreases As the distance from the source increases, most materials do not attenuate magnetic fields.
They take place both naturally and due to human activity. Natural electromagnetic fields are, for example, the static magnetic field of the earth to which we are continually exposed, electric fields caused by electrical charges present in clouds , static electricity that occurs when two objects rub against each other, or electric fields and sudden magnetic resulting from the rays.
Electromagnetic fields of human origin are, for example, generated by extremely low frequency (FEB) sources such as power lines, wiring and household appliances , as well as by higher frequency sources, such as radio and television waves or, more recently, from mobile phones and their antennas.
Biological effects and health effects
Exposure to electromagnetic fields is not a new phenomenon. However, in the 20th century, environmental exposure has continuously increased as the growing demand for electricity, the constant advancement of technologies and changes in social habits have generated more and more artificial sources of electromagnetic fields.
We are all exposed to a complex combination of weak electric and magnetic fields, both at home and at work, from those that produce electricity generation and transmission, household appliances and industrial equipment, to those produced by telecommunications and broadcasting. radio and television.
Tiny electrical currents are produced in the body due to chemical reactions from normal bodily functions, even in the absence of external electrical fields. For example, nerves emit signals by transmitting electrical impulses. In most biochemical reactions, from digestion to brain activities, a reorganization of charged particles occurs. Even the heart has electrical activity, which doctors can detect by electrocardiograms .
Low-frequency electric fields influence the body, as in any other material made up of charged particles. When electric fields act on conductive materials, they affect the distribution of electrical charges on the surface. They cause a current that goes through the body to the ground.
Low frequency magnetic fields induce circulating currents in the body. The intensity of these currents depends on the intensity of the external magnetic field. If it is strong enough, the currents could stimulate the nerves and muscles or affect other biological processes.
Both electric and magnetic fields induce electrical stresses and currents in the body, but even just below a high-voltage electricity transmission line the induced currents are very small compared to thresholds for the production of electric shocks or other electrical effects .
The main biological effect of radio frequency electromagnetic fields is heating. This phenomenon is used in microwave ovens to heat food. The levels of radio frequency fields to which people are normally exposed are much lower than necessary to produce significant warming. The current guidelines are based on the heating effect of radio waves.
Scientists are also investigating the possibility of long-term exposure effects below the threshold for body warming. To date, no adverse health effects have been confirmed due to long-term exposure to low intensity fields of radio frequency or network frequency, but scientists continue to actively investigate in this field.
Biological effects are measurable responses to a stimulus or change in the environment. These changes are not necessarily harmful to health. For example, listening to music, reading a book, eating an apple, or playing tennis are activities that produce various biological effects. However, we do not expect any of these activities to produce health effects.
The organism has complex mechanisms that allow it to adjust to the many and varied influences of the environment in which we live. Continuous change is part of our normal life, but, of course, the organism does not have adequate mechanisms to compensate for all the biological effects. Irreversible changes that force the system for long periods can pose a health hazard.
A detrimental health effect is one that causes a detectable dysfunction in the health of exposed persons or their descendants; on the contrary, a biological effect may or may not produce a detrimental effect on health .
It is not disputed that above certain thresholds, electromagnetic fields may trigger biological effects. According to experiments carried out with healthy volunteers, short-term exposure to levels present in the environment or at home do not produce any manifest harmful effect. Exposure to higher levels, which could be harmful, is limited by national and international guidelines. The current controversy centers on whether or not low levels of long-term exposure can elicit biological responses and influence people’s well-being.
Electromagnetic fields activate the body’s stress response, causing changes in almost all of its functions, including a significant decline in the immune systems . Other negative effects of EMFs include a negative impact on the cardiovascular , endocrine , growth control, and central nervous systems .
Researchers have found that prolonged exposure to low-level magnetic fields, such as those generated by hair dryers, coffee makers, and electric blankets, can damage DNA in brain cells. Continuous exposure has also been found to cause cells to self-destruct because they cannot repair themselves. The study suggests that the effects are cumulative, meaning that duration can be as damaging as intensity.