Electric current
Technological usage of electric current – wired and wireless

Man-made occurrences of electric current include the controlled flow of conduction electrons in metal wires, such as overhead power lines for long-distance energy delivery and the smaller wires within electrical and electronic devices. Eddy currents are electric currents that occur in conductors exposed to changing magnetic fields. Similarly, electric currents occur, particularly in the surface, of conductors exposed to electromagnetic waves. When oscillating electric currents flow at the correct voltages within radio antennas, radio waves are generated.

Pantographs are an example of electricity transfer through a sliding contact. The pantograph has enabled large-scale electrification of railways, subway and tram networks, as well as networks of trolleybuses.

Subsea interconnectors enable large-scale coast-to-coast electricity transfer between countries.

In electronics, other forms of electric current include the flow of electrons through resistors or through the vacuum in a vacuum tube, the flow of ions inside a battery, and the flow of holes within metals and semiconductors.

A newly developed use of electric current is wireless charging of batteries, for use in phones and electric vehicles for instance. Poynting's theorem shows that electric energy can be transferred from A to B, without carrying current from A to B. This is achieved by using one or more coils in A. The coils generate an electromagnetic field that carries the electric energy to B. Wireless charging devices could potentially be integrated in furniture, walls or road surfaces. Currently research is being done in long-distance wireless charging.
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