ELF electrical fields
ELF electrical fields are the result of an electrical voltage applied across wiring,
installations, and appliances when connected to the grid or plugged into an outlet—even when no current flows.
The strength of a given electrical field is determined by the voltage of the grid*. Generally,
the voltage of residential wiring systems is 230/400 volts (120/240 V in North America), medium voltage 20 kV (1 kilovolt = 1,000 volts), and high voltage 110-380 kV.
Voltage—or more precisely, the potential difference—is measured in volt (V). A thousandth of a volt is as a millivolt (mV).
The strength of the ELF electrical field is measured in volt per meter (V/m),
ELF magnetic fields
ELF magnetic fields are the result of an electrical current that flows through appliances that are turned on, cables, railway transmission lines, and high-voltage power lines.
The higher this current is and the farther apart the conductors are spaced, the higher the resulting field will be. In other words: the field strength* varies according to the strength of the electrical current and the spacing as well as the positioning of the conductors.
The magnetic field strength is measured in ampere per meter (A/m), the magnetic flux density in tesla (T). A millionth of a tesla is a microtesla (µT), a billionth a nanotesla is a nanotesla (nT).