In Figure 1, we immediately know that the flux density vector points in the positive z direction inside the solenoid, and in the negative z direction outside the solenoid. This is a derivation of the magnetic flux density around a solenoid that is long enough so that fringe effects can be ignored. The magnetic field inside an infinitely long solenoid is homogeneous and its strength neither depends on the distance from the axis nor on the solenoid's cross-sectional area. 'Continuous' means that the solenoid is not formed by discrete finite-width coils but by many infinitely thin coils with no space between them in this abstraction, the solenoid is often viewed as a cylindrical sheet of conductive material. Integrating over path c demonstrates that the magnetic field inside the solenoid must be radially uniform.Īn infinite solenoid has infinite length but finite diameter. In engineering, the term ' solenoid' refers not only to the electromagnet but to a complete apparatus providing an actuator that converts electrical energy to mechanical energy.įigure 1: An infinite solenoid with three arbitrary Ampèrian loops labelled a, b, and c. These solenoids, focus coils, surround nearly the whole length of the tube. Electrons take helical paths within the magnetic field.

Solenoids provide magnetic focusing of electrons in vacuums, notably in television camera tubes such as vidicons and image orthicons.

The helical coil of a solenoid does not necessarily need to revolve around a straight-line axis for example, William Sturgeon's electromagnet of 1824 consisted of a solenoid bent into a horseshoe shape (not unlike an arc spring).

The term solenoid was coined in 1823 by André-Marie Ampère. The coil can produce a uniform magnetic field in a volume of space when an electric current is passed through it. Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field linesĪ solenoid ( / ˈ s oʊ l ə n ɔɪ d/ ) is a type of electromagnet formed by a helical coil of wire whose length is substantially greater than its diameter, which generates a controlled magnetic field.

Electric solenoid valve 220v