What Is Electromagnetic Field (EMF)?

There are various kind of electromagnetic fields (EMF, electromagnetic waves) in our daily life. For example, “visible light” is one of the forms of electromagnetic fields and this includes lighting, however, most of electromagnetic fields are neither visible nor detectable by human senses.

During use of a home appliance, electric current flows when plug it into power outlet and switch is on. Flow of electric current generates both “electric field” and “magnetic field” simultaneously. The space within which these electric and magnetic fields coexist is called “electromagnetic field (EMF)”. These fields, in turn, propagate through space as waves known as “electromagnetic waves”.

Electric Field

Electric field is a space (place) within which electrical forces are present.

It arises due to differences in potential. For example, electric voltage always applies in the cord of home appliance with its plug into a power outlet, resulting in the generation of an electric field even when the switch is off.

The strength of the electric field is measured in volts per meter (V/m) as it depends on electric voltage. In general, the intensity of electric field rapidly decreases with the distance from the source.

Electric fields always surround us. For example, we feel weak electric shock when touching door knob in winter, or our clothes cling to us during dry seasons. These occurrences are the phenomena caused by occurrence of static electric field due to dryness and friction.

Magnetic Field

Magnetic field is a space (place) within where magnetism is present.

It is generated by the flow of electric current. For example, electric voltage is always present in the cord of home appliance when plug into a power outlet, resulting in the generation of an electric field even when the switch is off. However, magnetic field is not generated until the switch is turned on and electric current begins to flow.

As the magnetic field depends on electric current, the unit of A/m (ampere per meter) is used, however, in general, magnetic flux density is commonly described using the unit T (tesla). Additionally, another unit of G (gauss) is used in some countries such as the United States of America. In general, the intensity of the magnetic field rapidly decreases with the distance from the source.

Magnetic field always exists in our surroundings. For example, the Earth is considered as a huge magnet, creating the magnetic field known as the geomagnetic field within our living environment. Additionally, magnetic field also are present around magnets themselves.

Frequency

Electromagnetic waves consist of electric and magnetic fields propagating through space, forming an electromagnetic field. Frequency refers to the count of peak-to-trough pair of the wave per second, and the unit of Hz (hertz) is used.

Electromagnetic fields generated from home appliances have frequencies of 50 Hz in the eastern part and 60 Hz in the western part of Japan. This means that electromagnetic fields are generated 50 and 60 times per second, respectively. As the frequency increases, the wavelength of the electromagnetic filed shortens.

• This figure illustrates the frequency of 3 Hz.
• For 50 Hz, the waves occur 50 times per second.

Ionizing Radiation/Non-Ionizing Radiation

All the electromagnetic fields present in our environment are broadly classified into ionizing and non-ionizing radiation.

Ionizing radiation possesses extremely high energy, enabling it to pass through materials or ionizing atoms and molecules (separate electrons from the nucleus).

High-energy ionizing radiation, such as X- and Gamma-rays, can induce mutations (including cancer) by damaging DNA, which contains genes. So that they are utilized under the strictly controlled environments, mainly for medical purposes.

On the other hand, low-frequency electromagnetic field (generated from electric power facilities like power lines and home appliances), intermediate-frequency electromagnetic field (generated from such as induction hobs) and high-frequency electromagnetic field (radio waves) (like radio waves used for TV/radio broadcasting, mobile telecommunications, etc.) do not have enough energy to ionize materials. Consequently, they are classified as non-ionizing radiation. Therefore, theoretically, they do not cause mutation (including cancer).

Unit prefix
k: kilo (1,000 times), M: mega (1,000,000 times), G: giga (1,000,000,000 times), T: tera (1,000,000,000,000 times), P: peta (1,000,000,000,000,000 times)