Electric and Magnetic Fields (EMF)

Information Resources

  • What are Electric and Magnetic Fields (EMF)?
  • News and Research
  • Publications from MREC and other sources
  • MREC Conference Presentations
  • Organizations


What are Electric and Magnetic Fields (EMF)? *
Electric and magnetic fields are invisible areas of energy (also called radiation) that are produced by electricity, which is the movement of electrons, or current, through a wire. An electric field is produced by voltage, which is the pressure used to push the electrons through the wire, much like water being pushed through a pipe. As the voltage increases, the electric field increases in strength. Electric fields are measured in volts per meter (V/m). A magnetic field results from the flow of current through wires or electrical devices and increases in strength as the current increases. The strength of a magnetic field decreases rapidly with increasing distance from its source. Magnetic fields are measured in microteslas (μT, or millionths of a tesla).

Electric fields are produced whether or not a device is turned on, whereas magnetic fields are produced only when current is flowing, which usually requires a device to be turned on. Power lines produce magnetic fields continuously because current is always flowing through them. Electric fields are easily shielded or weakened by walls and other objects, whereas magnetic fields can pass through buildings, living things, and most other materials.

Electric and magnetic fields together are referred to as electromagnetic fields, or EMFs. The electric and magnetic forces in EMFs are caused by electromagnetic radiation. There are two main categories of EMFs:

  • Higher-frequency EMFs, which include x-rays and gamma rays. These EMFs are in the ionizing radiation part of the electromagnetic spectrum and can damage DNA or cells directly.
  • Low- to mid-frequency EMFs, which include static fields (electric or magnetic fields that do not vary with time), magnetic fields from electric power lines and appliances, radio waves, microwaves, infrared radiation, and visible light. These EMFs are in the non-ionizing radiation part of the electromagnetic spectrum and are not known to damage DNA or cells directly. Low- to mid-frequency EMFs include extremely low frequency EMFs (ELF-EMFs) and radiofrequency EMFs. ELF-EMFs have frequencies of up to 300 cycles per second, or hertz (Hz), and radiofrequency EMFs range from 3 kilohertz (3 kHz, or 3,000 Hz) to 300 gigahertz (300 GHz, or 300 billion Hz). Radiofrequency radiation is measured in watts per meter squared (W/m2).

What are common sources of non-ionizing EMFs?

There are both natural and human-made sources of non-ionizing EMFs. The earth’s magnetic field, which causes the needle on a compass to point North, is one example of a naturally occurring EMF. Human-made EMFs fall into both the ELF and radiofrequency categories of non-ionizing part of the electromagnetic spectrum. These EMFs can come from a number of sources.

Extremely low frequency EMFs (ELF-EMFs). Sources of ELF-EMF include power lines, electrical wiring, and electrical appliances such as shavers, hair dryers, and electric blankets.

Radiofrequency radiation. The most common sources of radiofrequency radiation are wireless telecommunication devices and equipment, including cell phones, smart meters, and portable wireless devices, such as tablets and laptop computers.

*Thank you to the National Cancer Institute for this description of electromagnetic fields.

The following is a broad range of information resources intended to increase your understanding of electric and magnetic fields (EMF). Should you have information to contribute to this Web page, please contact the MREC at mrec@cals.wisc.edu.

News and Research

UK regulatory agency finds Stetzer’s promotion of EMF-blocking product unfounded

Stetzer Electric Inc., one of WI’s well-known alternative stray voltage consultants, received a negative ruling in the UK. Advertisements of a product they claimed to “absorb dangerous dirty electricity from the wiring in buildings” were found by the UK’s Advertising Standards Authority (ASA) to be unsubstantiated and ordered to be removed from publication.  Click here to read a summary of the ASA’s ruling. (Reference A12-210702, 1/16/13).

Publications from MREC and other sources

MREC Conference presentations on electromagnetic fields:

Organizations with information and resources on electromagnetic fields: