Solenoid Theory

These first few posts will focus on the design theory behind transmission solenoids:

Solenoid theory:

  • A solenoid coil creates magnetic energy.
  • The strength of the solenoid comes from its coil.
  • Coil is made of magnet wire.
  • The magnetic energy is referred to as magnetic flux.

Magnetic flux theory:

When electricity flows through a conductor, a very small, magnetic field is generated around the wire. This magnetic field is measured in terms of its’ magnetic flux (measured in a unit called Maxwells). This magnetic flux will travel in small circles around the wire.

Now if several wire are placed together, with the current flowing through them, the magnetic field will begin to encircle all the wires. When the flux measured around any cross sectional area it is then termed magnetic flux density. (The unit is Gauss) .

The closer the wires, and the more wires that are present will result in a higher magnetic flux density.

A diagram showing magnetic fields around a solenoid

Magnetic flux travels about the entire solenoid.

Magnetic theory, the solenoid:

Looking at a solenoid coil, the magnetic flux travels about the entire solenoid as shown in the picture.

The strongest magnetic flux density is in the center where the line are closest together. All of the magnetic flux is forced to flow through this area. When no more flux can pass through the center, it has become magnetically saturated.

Each component in the solenoid gets polarized with it’s own north and south pole. This creates the magnetic attraction between solenoid components.

The amount each part gets magnetized depends on the components material composition. i.e. steels get magnetized, brass, does not.

The solenoid enclosure, can, helps to direct these lines of flux to the proper areas of the solenoid.


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