Electric and Magnetic Fields
Electric and magnetic fields (EMFs) are invisible lines of force that surround all electrical wiring and devices. Also know as electromagnetic radiation (EMR), they are associated with the generation, transmission, and use of electric power and emanate from a number of sources which surround our everyday lives.
- The power lines outside which tower above us or are hidden underground.
- The electrical wiring hidden within the walls of our homes and offices that connect all of the outlets, lights, and light switches to the main power.
- The cords and extension cords that connect all of our electric and electronic equipment, appliances, lamps, and anything else we plug into the walls. [pictures – electric cords, octopus]
- The motors and heating coils in electric equipment and appliances, large and small, from refrigerators to hair dryers.
Electric fields are produced by voltage and increase in strength as the voltage increases. This means that electric fields are often present even when the equipment is switched off, as long as it remains connected to the source of electric power.
Magnetic fields result from the flow of current through wires or electrical devices and increase in strength as the current increases. Most electrical equipment has to be turned on for a magnetic field to be produced, however, some of today’s electronic equipment with stand-by mode continues to draw current and produce magnetic fields when they are not in use.
Both electric fields and magnetic fields decrease rapidly as the distance from the source increases. The decrease follows the square of the distance, so a good rule of thumb is that the field strength is only a quarter when you double the distance from the source. Therefore, the first line of reducing EMF exposure is always to increase the distance from the source.
Electric fields can be shielded or weakened by materials that conduct electricity, even by materials that are poor conductors, like trees and walls. Magnetic fields, however, pass through most materials and are therefore more difficult to shield. Therefore, in a typical home or office environment, magnetic field shielding is hardly ever a realistic option.
The electric power that we use in our grid is based on alternating current or AC power. The voltage along the line alternates in polarity as a sine wave. The frequency of this oscillation is either 50 or 60 Hz (Hertz) depending on the country. Hertz is a unit defined as the number of cycles per second.
Although this may seem fast, this frequency range is very low in the electromagnetic spectrum and the electromagnetic fields that are produced in this range are therefore referred to as Extremely Low Frequency or ELF radiation.