What is a solenoid?
A solenoid is a type of electromagnet which consists of coil of wire in a helical shape. It becomes a magnet when electric current pass through it. Usually, a movable metallic core, of ferromagnetic material such as iron is inserted into this helical coil. The magnetic field of this helical coil interacts with the metallic material and hence causes this metal to move. This movable metal is commonly known as plunger.
Therefore a solenoid is used to convert an electrical energy into linear mechanical motion which is why it has numerous applications in different machines.
How it works?
In a solenoid, a coil of wire is connected to a power source typically to a battery. When the switch is closed between the battery and the solenoid coil, the electric current passes through the coil or alternatively we can say that the solenoid coil is energized.
According to Ampere’s Law, this passing of electric current produces a magnetic field around the coil.
The strength of magnetic field depends upon the number of turns in the coil and the strength of current. Moreover the magnetic field inside the coil is uniform inside the coil and resemble the magnetic field of bar magnet with well define North and South pole.
When the solenoid is energized, a magnetic field is produced (as highlighted in blue) by the helical coil.
When the solenoid coil is energized, it pushes or pulls the plunger (metal part inside the coil) depending upon how the it is aligned with the magnetic field of the coil. It is because of this linear motion of the plunger that solenoid find many applications in various domains.
Application of Solenoid
Since solenoid is capable of generating a linear mechanical motion there it is used as an actuator in various types of valves to control the flow of the fluid.
Additionally due to the ability of solenoid to generate binary output (on and off position), it has numerous uses as switching mechanism such as in automatic door locks .