A branch of physics deals with electric current or fields and magnetic fields and their interaction on substance or matter is called Electromagnetism. Electromagnetism has created a great revolution in the field of engineering applications. In addition, this caused a great impact on various fields such as medical, industrial, space, etc.
We can find enormous practical application of electromagnetism in everyday life from domestic appliances to research applications.
In domestic applications we can observe the phenomena in lighting, heating and kitchen appliances , in communication systems this exist in all telecommunication equipments and communication networks , in industrial systems this can be applied in motors, generators, sensor and actuator devices, etc.
If a current carrying conductor wound on a high permeability core (or iron core) creates an electromagnet. If this electromagnet is excited with a source of supply, then the magnetic field is produced. The strength of the magnetic flux depends on the current flowing through the electromagnet and the number of turns wounded on it.
Although all current carrying conductors produce magnetic fields, an electromagnet is specially constructed to maximize the strength of the magnetic field for a specific function.
The magnetic fields produced by electromagnets used for special functioning of the devices. Such devices include transformers, relays, motors, etc. In transformer the magnetic field produced causes the emf to generate in secondary coil such that voltage transfer is carried between two magnetically coupled circuits.
In case of relays, the magnetic field produced caused the plunger movement so that contacts get closed or opened and in motors this field causes the motor to rotate in a specific direction. Therefore, the usage of electromagnetism is wide and everywhere. So let us discuss some of the application areas where electromagnetism is used.
Electromagnetism serves as a basic principle of working for many of the home appliances in household applications. These applications include lighting, kitchen appliances, air conditioning systems, etc.
- The most dominant use of power in homes as well as commercial buildings is lighting systems. These lighting systems used numerous fluorescent lighting fixtures. Ballasts used in the fluorescent lamps use electromagnetism principle so that at the time of turn ON of the light it produces a high voltage.
- Electric fans, blowers and other cooling systems use electric motors. These motors work on the principle of electromagnetic induction which is the branch of electromagnetism. In any electrical appliance, electric motor is moved by the magnetic field produced by the electric current according to the Lorenz force principle. These motors are vary in size, rating and cost based on the application.
- Kitchen appliances like induction cookers, microwave ovens, electric mixers and grinders, bread toasters, etc. use the electromagnetism for their operation.
- Alarming systems use electrical bells which works based on electromagnetic principle. In these bells, the sound is produced by electromagnetic coils which move the striker against the bell. As long as the coil is energized, iron striker gets attracted by it, hence it strikes the bell.
- The electromagnets will be demagnetized when the striker get contact with bell and by the spring tension striker comes back to its original position and again electrical contact will be made once again. This process repeats until the switch gets opened.
- Security systems use locking systems for doors which are generally magnetic locking systems. These systems are unlocked either by a magnetic card swiping or having a security code.
- Magnetic card reader on the doors reads the number of keys stored in the magnetic tape of the card. When key stored in memory matches with data on the card, then the door opens.
- Entertainment system like television, radio or stereo systems use loudspeaker. This device consists of electromagnet which is attached to the membrane or cone surrounded by the magnetic flux produced by the permanent magnet.
- When the current through the electromagnet is varied, electromagnet and membrane of the speaker get moved back and forth. If the current is varied at the same frequencies of the sound waves, results a vibration of the speaker which will further create sound waves.
Almost all of the instruments or devices used in industries are based on the electromagnetism. Materials used in constructing such devices include iron, cobalt, nickel, etc which naturally responds to the magnetic fields.
Starting from small control instruments to the large power equipments, the electromagnetism is used at least at one stage of their working.
- Generators and motors dominate in most of the industries which are the primary power source and driving systems respectively. Generators convert the mechanical to electrical energy whereas the motors convert electrical energy to mechanical energy.
- Generators supply the electrical energy in the time of mains power interruption and most of the cases, these are driven by the IC engines. There are different classes of motors which are employed in industries. These are used for cranes, hoists, lifts, conveyor systems, etc.
- Various sensors and actuating devices are works based on electromagnetism. Electromagnetic sensors include Hall-effect sensors, magnetoresistive sensors, fluxgate sensors, etc. These sensors convert the physical quantity such as flow, pressure, level, proximity, etc into an electrical signal.
- Actuators are the final control elements which drives the load at specific conditions. These actuator devices include solenoid valves, relays, motors, etc. and all these works on the principle of electromagnetism.
Magnetic Levitation Trains
This is the modern technology of transportation systems that use the concept of electromagnetism. These are called as high speed trains which use powerful electromagnets to develop the speed.
These trains will float over a guide way using the basic principles of magnets such as electromagnetic suspension (EMS) and electrodynamic suspension (EDS). In EMS, electromagnets employed on the train body are attracted to the iron rails.
These magnets wrap around the guided rails and attractive force between the guideways and magnets lifts the train upwards. In EDS, train is levitated by the repulsive force in the conductive guideways by induced currents.
A guideway is nothing but an arrangement of specially designed magnetic coils and tracks at regular intervals. Along this guideway a maglev train is suspended by the phenomenon of the magnetic levitation with no supports other than magnetic fields.
The above figure shows the EMS magnetic levitation system in which electromagnets are attached to the body of the train and are powered by the batteries in the train. The guideway consists of electromagnetic coils built on the surface of the track.
These coils are constructed with core material and coil windings. When the electromagnets are energized, the train will be levitated by the attractive force between the electromagnets and the coils.
Hence this type of systems needs a large electrical power source, electromagnetic coils lining a guideway and guidance magnets attached to the underside of the train.
It is the process of transmitting information from a source to a receiver. This transmission of energy over long distances is carried out through electromagnetic waves at high frequencies. These waves are also called as microwaves or high frequency radio waves.
Suppose in case of mobile phones, sound energy is converted into electromagnetic energy. By using radio transmitters, this electromagnetic energy is transferred to the receiver. At the receiver these electromagnetic waves are again transformed back into sound energy.
Depending on the nature of the baseband signal, communication systems can be analog or digital communication systems. Depending on the nature of transmitting signal, this system is categorized as baseband and carrier communication systems.
Electromagnetic fields produced by the time varying sources are propagated through a waveguide or transmission line. An electromagnetic wave radiation is formed when these electromagnetic fields are propagated away from the sources without any connection or conducting medium to the sources.
An electromagnetic spectrum consists of different range of all possible wavelength or frequencies of electromagnetic radiation. These frequency ranges include low frequency, ultra low frequency, medium frequency, high frequency, ultra high frequency, super high frequency etc.
Nowadays electromagnetic fields play a key role in advanced medical equipments such as hyperthermia treatments for cancer, implants and magnetic resonance imaging (MRI).
RF range frequencies are mostly used in medical applications. In MRI scans, sophisticated equipment works based on the electromagnetism can scan minute details of the human body.
The electromagnetic therapy is an alternate form of medicine which claims to treat disease by applying pulsed electromagnetic fields or electromagnetic radiation to the body. This type of treatments is used for wide range of ailments such as nervous disorders, diabetes, spinal cord injuries, ulcers, asthma, etc.
Many of the medical equipments such as scanners, x-ray equipments and other equipments uses electromagnetism principle for their functioning.