sOLENOID is an electromagnetic device which produces magneti c field whe n current i s pass ed throughits coil windings. The term solenoid refers to a variety oftransducer devices t hat convert electrical energy into kinetic energy. A basic solenoid structure consists of anelectromagnetically inductive coil which is wound around a movable armature. In general, a solenoid’ s armature is also wide ly known as plunger and it is usuall y made fr om ferromagnetic materials like soft iron . The armature provides mechanical force for certain mechanis ms which is proporti onal to the change in inductance o f the coil wit h respect to the armature’s positi on and current flowing through the coil. The applied force will alway s move the armature in a direction t hat i ncreases t he coil ’s inductance. Basically, the armature will move into the solen oid when the co il windings are energized and thus create linear moti on.Solenoid generally creates linear moti on which is veryunique due to it s force – st roke characteristics. The forcevaries according to the stroke length which provides a wide range of ene rgy band for the solenoid to operate. The range of energy band allows selection for t he user t o operate the solen oid with optimum performance and efficiency. Classi cally, there are two types of armature topologies, flat and conical. The flat-type solen oid generall y provides large force in a range where the dis placement or stroke is small. Whereas the cone- type solenoid provides approximately flat-curv e force characteristics regardless of the dis placement as compared t o flat face solenoid, this makes the conical solen oid effective in usage wit h a medium driving path(s troke). Solen oid can be push type or pull type depending on the appli cation requirement. The angle of armature cone is decided based on the force and the stoke requirements for typ ical application to optimize the weight of the solen oid.Armature cone is decided based on the index number f or the typ ical application. Index number (i) is defined as the ratio of square root of the load force (lbf) to stroke (in) [1]. The relation between index number and armature cone angle; based on weight economy, is developed from practicalexperience [1].