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Encyclopedia > Solenoid
Magnetic field created by a solenoid

A solenoid is a 3-dimensional coil. A solenoid may refer to Solenoid in physics Solenoid (DNA) Solenoid (genetics) Solenoid (mathematics) Category: ... Image File history File links Broom_icon. ... Image File history File links Solenoid. ... Image File history File links Solenoid. ... A coil is a series of loops. ...

In physics, the term solenoid refers to a loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electrical current is passed through it. Solenoids are important because they can create controlled magnetic fields and can be used as electromagnets. The term solenoid refers specifically to a magnet designed to produce a uniform magnetic field in a volume of space (where some experiment might be carried out). A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... This article is about metallic materials. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... An electromagnet is a type of magnet in which the magnetic field is induced by a flow of electric current. ...

In engineering, the term solenoid may also refer to a variety of transducer devices that convert energy into linear motion. The term is also often used to refer to a solenoid valve, which is an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch; for example, an automobile starter solenoid, or a linear solenoid, which is an electromechanical solenoid. Engineering is the applied science of acquiring and applying knowledge to design, analysis, and/or construction of works for practical purposes. ... A transducer is a device, usually electrical or electronic, that converts one type of energy to another. ... A solenoid valve is an electromechanical valve for use with liquid or gas controlled by running or stopping an electrical current through a solenoid, which is a coil of wire, thus changing the state of the valve. ... Pneumatics, from the Greek πνευματικός (pneumatikos, coming from the wind) is the use of pressurized air in science and technology. ... Hydraulics is a branch of science and engineering concerned with the use of liquids to perform mechanical tasks. ... Automotive style miniature relay A relay is an electrical switch that opens and closes under the control of another electrical circuit. ... Starter solenoid is a part of an automobile ignition system. ...


Derivation of magnetic field around a long solenoid

This is a derivation of the magnetic field around a solenoid, that is long enough so that fringe effects can be ignored.

A solenoid with 3 Ampèrian loops
A solenoid with 3 Ampèrian loops

In the diagram to the right, we immediately know that the field points in the positive z direction inside the solenoid, and in the negative z direction outside the solenoid. We see this by applying the right-hand rule for the field around a wire. If we wrap our right hand around a wire with the thumb pointing in the direction of the current, the fingers show how the field behaves. Since we are dealing with a long solenoid, all of the components of the magnetic field not pointing upwards cancel out by symmetry. Outside, a similar cancellation occurs, and the field is only pointing downwards. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ...

Now consider loop "c". By Ampère's law, we know that the path integral of B around this loop is zero, since no current passes through it. We have shown above that the field is pointing upwards inside the solenoid, so the horizontal portions of loop "c" don't contribute anything to the integral. Thus the integral up side 1 is equal to the integral down side 2. Since we can arbitrarily change the dimensions of the loop and get the same result, the only physical explanation is that the integrands are actually equal, that is, the magnetic field inside the solenoid is constant. A similar argument can be applied to loop "a" to conclude that the field outside the solenoid is constant. An electric current produces a magnetic field. ...

A solenoid with a looping magnetic field line
A solenoid with a looping magnetic field line

An intuitive argument can be used to show that the field outside the solenoid is actually zero. Magnetic field lines only exist as loops, they cannot diverge from or converge to a point like electric field lines can. The magnetic field lines go up the inside of the solenoid, so they must go down the outside so that they can form a loop. However, the volume outside the solenoid is much greater than the volume inside, so the density of magnetic field lines outside is greatly reduced. Recall also that the field outside is constant. In order for the total number of field lines to be conserved, the field outside must go to zero as the solenoid gets longer. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ...

Now we can consider loop "b". Take the path integral of B around the loop, with the height of the loop set to L. The horizontal components vanish, and the field outside is zero, so Ampère's Law gives us:

BL = μ0NI

From which we get:

B = μ0NI/L

Rotary Voice Coil

This is a rotational version of a solenoid. Typically the fixed magnet is on the outside, and the coil part moves in an arc controlled by the current flow through the coils. Rotary voice coils are widely employed in devices such as disk drives.

Electromechanical solenoids

Electromechanical solenoids consist of an electromagnetically inductive coil, wound around a movable steel or iron slug (termed the armature). The coil is shaped such that the armature can be moved in and out of the center, altering the coil's inductance and thereby becoming an electromagnet. The armature is used to provide a mechanical force to some mechanism (such as controlling a pneumatic valve). Although typically weak over anything but very short distances, solenoids may be controlled directly by a controller circuit, and thus have very low reaction times. For other uses, see Steel (disambiguation). ... For other uses, see Iron (disambiguation). ... An electric current i flowing around a circuit produces a magnetic field and hence a magnetic flux Φ through the circuit. ...

The force applied to the armature is proportional to the change in inductance of the coil with respect to the change in position of the armature, and the current flowing through the coil. The force applied to the armature will always move the armature in a direction that increases the coil's inductance.

The magnetic field inside a solenoid is given by:

B = μ0nI = μ0(N / L)I

where mu_0=4pi times 10^{-7} henries per metre, B is the magnetic field magnitude in teslas, n is the number of turns per metre, I is the current in amperes, N is the number of turns and L is the length of the solenoid in metres. See also: Electromagnet. For other uses, see Ampere (disambiguation). ... An electromagnet is a type of magnet in which the magnetic field is produced by a flow of electric current. ...

Electromechanical solenoids are commonly seen in electronic paintball markers, dot matrix printers and fuel injectors. A paintball marker, also known as a paintball gun, is the central piece of equipment in the sport of paintball. ... A dot matrix printer or impact matrix printer refers to a type of computer printer with a print head that runs back and forth on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like a typewriter. ... // Fuel injection is a means of metering fuel into an internal combustion engine. ...

Pneumatic solenoid valves

A pneumatic solenoid valve is a switch for routing air to any pneumatic device, usually an actuator of some kind. A solenoid consists of a balanced or easily moveable core, which channels the gas to the appropriate port, coupled to a small linear solenoid. The valve allows a small current applied to the solenoid to switch a large amount of high pressure gas, typically up to 100 psi (7 bar, 0.7 MPa, 0.7 MN/m²). Some solenoids are capable of operating at far greater pressures. A solenoid valve is an electromechanical valve for use with liquid or gas controlled by running or stopping an electrical current through a solenoid, which is a coil of wire, thus changing the state of the valve. ... An actuator is a mechanical device for moving or controlling a mechanism or system. ...

Pneumatic solenoids may have one, two, or three output ports, and the requisite number of vents. The valves are commonly used to control a piston or other linear actuator.

The pneumatic solenoid is akin to a transistor, allowing a relatively small signal to control a large device. It is also the interface between electronic controllers and pneumatic systems. Assorted discrete transistors A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. ...

Hydraulic solenoid valves

Hydraulic solenoid valves are in general similar to pneumatic solenoid valves except that they control the flow of hydraulic fluid (oil), often at around 3000 psi (210 bar, 21 MPa, 21 MN/m²). Hydraulic machinery uses solenoids to control the flow of oil to rams or actuators to (for instance) bend sheets of titanium in aerospace manufacturing. Solenoid-controlled valves are often used in irrigation systems, where a relatively weak solenoid opens and closes a small pilot valve, which in turn activates the main valve by applying fluid pressure to a piston or diaphragm that is mechanically coupled to the main valve. A solenoid valve is an electromechanical valve for use with liquid or gas controlled by running or stopping an electrical current through a solenoid, which is a coil of wire, thus changing the state of the valve. ... Excavator. ...

Transmission solenoids control fluid flow through an automatic transmission and are typically installed in the transmission valve body. A transmission solenoid is an electro-hydraulic valve that controls fluid flow into and throughout an automatic transmission. ...

Solenoids in fiction

The use of the word solenoid (particularly in science fiction) could be grouped in with other terms such as conduit, socket, firewall, capacitor, wormhole and laser to lend some kind of scientific/engineering credibility from a layman's perspective. Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... A conduit is a general term for a means of conveying something from one location to another or between persons. ... The Berkeley sockets application programming interface (API) comprises a library for developing applications in the C programming language that perform inter-process communication, most commonly across a computer network. ... This article is about the network security device. ... See Capacitor (component) for a discussion of specific types. ... For other uses, see Wormhole (disambiguation). ... For other uses, see Laser (disambiguation). ...

  • In the anime and manga series Neon Genesis Evangelion, one plot device was a "Super Solenoid Engine" (or S²), a limitless power source.
  • In Steven Spielberg's 2005 War of the Worlds movie, the alien tripods disable all flow of electric current in a wide area, thus rendering vehicles useless; the problem is fixed by replacing the solenoid.
  • In Gene Roddenberry's Andromeda TV-Series, an Anti-Proton Solenoid Valve is used to control the flow of the anti-protons which are used to power the ship and propel it through space. In the Episode "The Vault of The Heavens" (3.18), Engineer Harper orders Trance to shut it, filling the Anti Proton tanks to capacity, then expelling it quickly, thereby accelerating the ship much more than normal.
  • In GUNNM, Sechs and Alita use coilguns, which makes use of solenoids to accelerate projectiles to supersonic speed. The result is a gun that can still cause major damage even if it misses. Alita's fires a rocket slug which has incredibly high power; Sechs' modified gun can fire multiple rounds in quick succession.

The Neon Genesis Evangelion franchise is a multi-billion dollar umbrella of Japanese media properties generally owned by the anime studio Gainax. ... NERV redirects here. ... Steven Allan Spielberg (born December 18, 1946)[1] is an American film director and producer. ... War of the Worlds is a 2005 science fiction disaster film based on H. G. Wells original novel starring Tom Cruise. ... Martian tripods drawn by Warwick Goble. ... Eugene Wesley Roddenberry (August 19, 1921 – October 24, 1991) was an American scriptwriter and producer. ... Gene Roddenberrys Andromeda is an American science fiction television series, based on unused material by Gene Roddenberry developed by Robert Hewitt Wolfe, and produced posthumously by his widow, Majel Roddenberry. ... Battle Angel Alita, known in Japan as GUNNM (銃夢), is a manga series created by Yukito Kishiro in 1991 which ended in 1995. ... A coilgun (not to be confused with a railgun) is a type of cannon which uses one or more electromagnetic coils to accelerate a magnetic projectile to high velocity. ...

External links

  Results from FactBites:
Solenoids as Magnetic Field Sources (242 words)
A long straight coil of wire can be used to generate a nearly uniform magnetic field similar to that of a bar magnet.
Such coils, called solenoids, have an enormous number of practical applications.
This turns out to be a good approximation for the solenoid field, particularly in the case of an iron core solenoid.
Solenoid Valves - Solenoid Valve Manufacturers - Pneumatic Solenoid Valves - Plastic Solenoid Valves (1506 words)
Solenoid valves are electro-mechanical devices that use a wire coil and a movable plunger, called a solenoid, to control a particular valve.
Their most common use is as solenoid water valves, oil valves, gas valves, steam valves, solvents valves, cryogenics valves, air and vapors valves, as well as many other applications as hydraulic valves and pneumatic valves.
Because solenoid valves are designed to perform operations, ranging from water valves, air valves, pneumatic valves or used in applications such as ones to restrict, meter and maintain the flow of liquid and gaseous materials, they are widely used in vastly different fields and industries.
  More results at FactBites »



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