What is solenoid?

What Does solenoid Mean

The solenoid is the name of the coil that, due to its design, generates a magnetic field of great intensity . This cylindrical coil has a conductive wire that is wound in such a way that the current causes the formation of an intense magnetic field. It is worth mentioning that in its etymology we find the union of two terms of Greek origin that can be translated as "tube-shaped", which is consistent with the appearance of the solenoid.

The current circulates through the conductive wire of the solenoid and the field is generated: the more extensive the coil, the more uniform the field is inside. According to the core , the solenoid can act as an electromagnet .

The solenoid is used in a class of valve called a solenoid valve . The opening and closing of these valves are produced by electrical pulses and can be controlled, in certain cases, by means of a program .
We can find solenoids in cars . The vehicle's starter solenoid , when the key is turned, is coupled to the starter motor through a shaft and manages to generate the movement necessary for the engine to turn.
This solenoid, therefore, receives current when the key turns; said current begins the procedure to force the start, including actions on a piston, a pinion and the crankshaft of the engine. Once the engine starts to turn, the reaction of the fuel allows it to generate its own energy. In this way, turning the crankshaft is no longer necessary.
It should be noted that when the key goes from "start" to the "on" position , the solenoid is deactivated. This means that the cylindrical coil stops sending current to the starter motor .
The most prominent benefit of using the solenoid can be seen when performing certain experiments in the field of physics, and it is the uniformity it offers, as mentioned in previous paragraphs. On the other hand, it also has some disadvantages, such as that it cannot generate a high magnetic field without a cooling system and expensive equipment , and that it is less direct than Helmholtz coils.
The Helmholtz coils , meanwhile, have circular shape and share the same axis and the same level of current flowing in one direction, and are used in laboratory techniques seeking a magnetic field of high uniformity. To make the central field as uniform as possible, the coils should be located at a distance from each other that equals their radius .
The French - born physicist and mathematician André-Marie Ampère , who was born at the end of the 18th century and lived until the middle of the 19th century, was the first person to coin the term solenoid, and he did so in the year 1820. At that time, it was found working on an experiment whose main theme was circular currents.

It does not happen so often to find an invention so old that it continues to have relevance today, especially if we consider that its use takes place in the field of science , where constant advances make many discoveries obsolete.
The formula for calculating the magnetic field in the middle third is: B = Mni / L . The variables involved in this equation are the magnetic permeability (m), the number of turns (N), the current that circulates (i) and the total length .
On the other hand, with these same elements it is possible to calculate the magnetic field of the extremes. To find this approximation it is necessary to make a single change: multiply the length of the solenoid by two before dividing the result by the product mNi .

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