Search

What are electric and magnetic fields and EMF's

Electric fields

Electric fields exist whenever a positive or negative electrical charge is present and exerts forces on other charges within a field. The standard unit for measuring electric field strength is volt per metre (V/m).


Here are some facts about electric fields:

  • Any charged electrical wire produces an associated electric field.

  • A field will exist even when there is no current flowing.

  • The higher the voltage, the stronger the electric field.

Electric fields are strongest when close to a charge or charged conductor, and their strength rapidly diminishes in proportion to the distance from the source. Other things that can impede the strength of the field include metal shields, walls, buildings, and trees. For example, electric fields around power lines are reduced within a home by walls and trees. Power lines buried underground will exert a barely detectable electric field.


Takeaway - Maintain the greatest distance between yourself and any electrical devices or sockets, especially power boards and your electric meter.


Magnetic fields

A magnetic field arises from the motion of electric charges. The most common unit for measuring magnetic field strength is in amperes per meter (A/m); or, more commonly in electromagnetic field research, scientists specify a related quantity, the flux density (in Microtesla, µT) instead.


Here are some facts about magnetic fields:

  • Unlike electric fields, a magnetic field exists when a device is on and produces a current flow. The higher the current, the greater the strength of the magnetic field.

  • The strength of magnetic fields do not diminish due to conventional materials such as the walls of buildings.

  • As with electric fields, magnetic fields are strongest when close to their origin and quickly decrease at distances further from the source.

Takeaway - For risk minimisation (as well as a lower power bill), unplug your electrical devices when not in use.


So, an electrical device that is off and plugged into an electrical socket will still have an electrical field. When it is turned on it will also then have a magnetic field. The only way for the electrical device to have no electrical or magnetic field is if it is turned off and the cord is removed from the electrical socket.


Wavelengths

One of the main characteristics defining an electromagnetic field (EMF) is its frequency or corresponding wavelength. Fields of different frequencies interact with the human body in different ways.


We have been lead to believe that Ionising Radiation (to the right of the graphic) is bad (and it is) and as you move left on the graphic it is safer. But the question is, how safe. Maybe no level is safe.

The electromagnetic spectrum in the diagram represents all of the possible frequencies of electromagnetic energy. It ranges from extremely long wavelengths at the left (extremely low-frequency exposures such as those from power lines) to extremely short wavelengths (x-rays and gamma rays) to the right and includes both non-ionising and ionising radiation. You can see the electromagnetic waves as being a series of very regular waves that travel at the speed of light. The frequency is the number of either oscillations or cycles per second where the wavelength is the distance between waves. Wavelength and frequency are intertwined; the lower the frequency the greater the wavelength, and the higher the frequency, the shorter the wavelength.


TYPES OF RADIATION


Ionising radiation - carries sufficient energy to detach electrons from atoms or molecules, thereby ionising an atom or a molecule


Non-ionising radiation - does not carry enough energy to ionize atoms or molecules—that is, to completely remove an electron from an atom or molecule


Source - Wikipedia



Electromagnetic fields

Electromagnetic fields form when a magnetic field (B) is coupled with an electric field (E). Magnetic and electrical fields of an electromagnetic wave are perpendicular to each other and the direction of the wave.