Umair Gaines
Electromagnetic induction, discovered by Michael Faraday in 1831, is a process where voltage or electric current is produced due to a changing magnetic field. This phenomenon is observed when a conductor is placed in a moving magnetic field or when a conductor is constantly moving within a stationary magnetic field. Faraday's law of electromagnetic induction mathematically describes the relationship between electricity and magnetism, where the induced voltage is directly proportional to the number of turns of the coil and the rate of change of the magnetic field. This principle is widely applied in everyday machines such as electric guitars, microphones, motors, generators, and transformers.
| Characteristics | Values |
|---|---|
| Discovery | Michael Faraday in 1831 |
| Mathematical description | James Clerk Maxwell as Faraday's law of induction |
| Process | A changing magnetic field induces a current in a current loop or a voltage across the ends of a current loop |
| Other names | Inductance, electromagnetic induction, electric induction |
| Applications | Electric generators, microphones, electric guitars, transformers, motors, credit card strips, etc. |
| Faraday's law | The induced voltage is directly proportional to the number of turns/coils of the wire |
| Eddy currents | Occur when a solid metallic mass is rotated in a magnetic field, causing a harmful rise in temperature |
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What You'll Learn
Faraday's Law of Induction
Michael Faraday, an English scientist, developed this law based on his experimental observations in 1831. He visualised a magnetic field as composed of many lines of induction, along which a small compass would point. The aggregate of these lines intersecting a given area is called the magnetic flux.
Faraday's first law of electromagnetic induction states that when a conductor is placed in a varying magnetic field, an electromotive force (emf) is induced. If the conductor circuit is closed, a current is induced, known as an induced current. This can be achieved by rotating the coil relative to the magnet, moving the coil into or out of the magnetic field, changing the area of the coil within the field, or moving a magnet towards or away from the coil.
Faraday's second law of electromagnetic induction quantifies the emf produced in the conductor. It states that the induced emf in a coil is equal to the rate of change of flux linkage, which is the product of the number of turns in the coil and the flux associated with the coil. The direction of the induced emf can be determined using Lenz's law, which describes the "flux through the circuit".
Faraday's law has many practical applications, such as in electrical equipment like transformers, induction cookers, electric guitars and violins, and in the functioning of electromagnetic flowmeters to record fluid velocity.
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Transformers and Inductors
The working of electrical transformers is based on electromagnetic induction, which was discovered by Michael Faraday in 1831. Faraday's law of induction states that the amount of voltage induced in a coil is directly proportional to the number of turns of the coil and the rate of change of the magnetic field. Transformers typically consist of two separate coils with different numbers of turns of conductor wound around the same closed laminated iron core. The primary winding is the coil in a transformer that is energised by the source, while the secondary winding is the coil connected to the load.
Inductors are two-terminal passive devices specifically designed to store magnetic energy, particularly at frequencies below a design-dependent upper limit. The four factors that determine or control the inductance of a coil are the cross-section of the core, the number of turns, the type of core, and the length of the coil. Inductors used at higher frequencies often have magnetic cores made of non-conductive magnetic materials such as ferrite or iron powder held together with a resin binder.
In summary, transformers and inductors are essential components in power distribution systems, with transformers facilitating the transfer of power between circuits and inductors storing magnetic energy.
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Eddy Currents
In electromagnetism, an eddy current is a loop of electric current induced within conductors by a changing magnetic field in the conductor, in accordance with Faraday's law of induction, or by the relative motion of a conductor in a magnetic field. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. They can be induced within nearby stationary conductors by a time-varying magnetic field created by an AC electromagnet or transformer, or by relative motion between a magnet and a nearby conductor.
The magnitude of the current in a given loop is proportional to the strength of the magnetic field, the area of the loop, and the rate of change of flux, and inversely proportional to the resistivity of the material. When graphed, these circular currents within a piece of metal resemble eddies or whirlpools in a liquid. Eddy currents can take time to build up and can persist for long periods in conductors due to their inductance.
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Electric Generators
The fundamental principles of electricity generation were further developed in the following decades, with the creation of the first practical electric generators, called dynamos. These machines used a coil of wire rotating in a magnetic field to produce an alternating current (AC). However, early uses of electricity often required direct current (DC), so commutators were used to convert the AC into DC. The dynamo was the first electrical generator capable of delivering power for industry, and it played a key role in the Second Industrial Revolution.
Overall, electric generators play a crucial role in the production and distribution of electricity, and their development has greatly impacted the field of electricity generation and our daily lives.
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AC Generators
Electromagnetic induction is the phenomenon where a changing magnetic field results in a potential difference or voltage in a conductor. Faraday's experiments showed that the size of the voltage produced within a conductor was proportional to the rate of change of the magnetic flux and the number of turns of the coil. This can be achieved by moving a conductor within a magnetic field or by moving a magnetic field around a conductor.
The basic principle behind AC generators is the conversion of mechanical energy to electrical energy. This requires an external torque to be applied to the rotor, turning it faster than the synchronous speed. The active power delivered to the line is proportional to the slip above the synchronous speed, with full-rated power typically reached at small slip values of around 3%.
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Frequently asked questions
Electromagnetic induction is a process where a change in magnetic field or voltage production (electromotive force) causes an electric current in a circuit loop or wire.
Michael Faraday discovered electromagnetic induction in 1831. He found that moving a magnet in and out of a coil or loop of wire induced an electric current or voltage.
Electromagnetic induction is used in electrical generators, microphones, electric guitars, and transformers. It is also involved when you swipe a credit card in a card machine.
Faraday's Law of Induction states that the electromotive force (EMF) in volts is equal to the number of turns of wire and the magnetic flux in Webers. This law describes the relationship between electricity and magnetism, where a changing magnetic field causes an induced current or voltage.
