The phenomenon of electromagnetism is broadly used in many electrical devices and in machines.
Some of the common uses of the electromagnetism are in:
Motors and Generators:
In small toy motors we use permanent magnets as the sources of the magnetic field, but in large industrial motors we use field coils which act as an electromagnet when a current is provided. These field coils in large motors then becomes the source of the magnetic field.
In electrical bells electromagnetic coils are used to move the striker against the bell to make sound. When the coil is energized, it will attract the iron striker, which strikes the bell. As soon as the striker moves toward the bell, the electrical contact will break and the electromagnet will be demagnetized. The striker after striking it is returned to its original position by the spring tension and the electrical contact will be made once again, thus the cycle will continues until the switch is in the open position.
Particle Acclerator : Cyclotron
The Cyclotron is a device used to accelerate charged particles to high energies.
A Cyclotron works on the principle that a charged particle moving normal to a magnetic field experiences magnetic Lorentz force due to which the particle moves in a circular path.
It consists of hollow metal cylinder divided into two sections D1 and D2 called dees, which are enclosed in an evacuated chamber. These dees perform the function of electromagnetism; they are provided with a continuous AC supply where the dees continuously change their polarity depending upon the frequency of the AC supply.
The dees are kept separated and source of ions is placed at the center in the gap between the dees. They are then placed between the pole pieces of a strong electromagnet. The magnetic field is perpendicular to the plane of the dees, and the dees are connected to a high frequency oscillator.
When a positive ion of charge q and mass m is emitted from the source, it is accelerated towards the dee having a negative potential at that instant of time.
Due to the normal magnetic field, the ion experiences a magnetic Lorentz force and moves in a circular path. By the time the ion arrives at the gap between the dees, the polarity of the dees get reversed. Hence the particle is once again accelerated and moves into the other dee with greater velocity along a circle of greater radius. Thus the particle moves in a spiral path or increasing radius and when it comes near the edge, it is taken out with the help of a deflector plate (DP). The particle with high energy is now allowed to hit the target T.
A Cyclotron is used to accelerate protons, deuterons, and alpha-particles.
Modern Application of Electromagnetism
Magnetic Levitation train:
The concept of electromagnetism is used in high speed maglev trains. They use power full electromagnetic force or EMF to provide both magnetic levitation of the train and propulsion.
The electromagnets which are fixed in the tracks perform two main functions. First, they have to magnetically levitate the train and make it to float in air, and second, another set of electromagnets helps to move the train by magnetic force.
Magnetic levitation is a phenomenon by which an object is suspended with no support other than magnetic fields. The magnetic pressure is used to neutralize the forces and effect of the gravitation.
In these specially designed tracks, electromagnetic coils for magnetic levitation are placed at regular intervals and are called a guideway. A set of large electromagnets or permanent magnets will be placed in the undercarriage of the train and will levitate the train 1 to 8 cm above the guideway. The guideway coil also helps to keep the train in track.
The propulsion coil will creating an alternating magnetic flux in the electromagnet so that the front part of the train will be attracted and back parts of the train will be in repulsion adding more force for the forward movement. Thus an alternating current is given to the propulsion coils creating a magnetic lock with the train. Thus the frequency of the alternating current is made to synchronize with the speed of the train.
Electro-magnetic Lifting Cranes:
Electromagnetic lifting cranes are used to lift and transport steel scraps, sheets, medium and thick plates, and steel bars. They use electromagnetism to magnetize the coil for lifting and demagnetize the electromagnetic coil for dropping the materials in the required place.
An electromagnetic container lifter works in the similar manner for transporting the container from the ship to port and vice versa.
Solenoid actuated valves:
Normally, these types of valves are used in the remote control operation for opening and closing the valves from the control station. This is achieved by solenoid coils which convert the electrical signal to a mechanical positioning of the valves.
The magnetization of the electromagnetic coils decides the valve positioning either to open or to close.
Parts of solenoid valve:
- Valve Body
- Inlet Port
- Outlet Port
- Coil / Solenoid
- Coil Windings
- Lead Wires