What are electric and magnetic fields?

Electricity is the movement of electrons, or current, through a wire. The type of electricity that runs through power lines and in houses is alternating current (AC). AC power produces two types of fields (areas of energy)-an electric field and a magnetic field. 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. A magnetic field results from the flow of current through wires or electrical devices and increases in strength as the current increases. These two fields together are referred to as electric and magnetic fields, or EMFs.
Both electric and magnetic fields are present around appliances and power lines. However, electric fields are easily shielded or weakened by walls and other objects, whereas magnetic fields can pass through buildings, humans, and most other materials. Since magnetic fields are most likely to penetrate the body, they are the component of EMFs that are usually studied in relation to cancer.
The focus of this fact sheet is on extremely low-frequency magnetic fields. Examples of devices that emit these fields include power lines and electrical appliances, such as electric shavers, hair dryers, computers, televisions, electric blankets, and heated waterbeds. Most electrical appliances have to be turned on to produce a magnetic field. The strength of a magnetic field decreases rapidly with increased distance from the source.
This answer is based on source information from the National Cancer Institute.

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