Trystan Casey
The term electricity is challenging to define comprehensively, with various definitions used in different contexts. Electrical induction, or electromagnetic induction, is the production of an electromotive force (emf) across an electrical conductor in a changing magnetic field. This process was discovered by Michael Faraday in 1831 and is described by Faraday's law of induction, which states that a voltage is induced in a circuit when there is relative motion between a conductor and a magnetic field. This phenomenon is the basis for the operation of electric generators, microphones, electric guitars, and transformers.
| Characteristics | Values |
|---|---|
| Process | The process by which an electrical conductor becomes electrified when near a charged body, by which a magnetizable body becomes magnetized when in a magnetic field or in the magnetic flux set up by a magnetomotive force, or by which an electromotive force is produced in a circuit by varying the magnetic field linked with the circuit |
| Discovery | Michael Faraday in 1831, and Joseph Henry in 1832 |
| Mathematical description | James Clerk Maxwell described it as Faraday's Law of Induction |
| Direction of induced field | Lenz's law |
| Generalized form | Maxwell-Faraday equation, one of the four Maxwell equations in his theory of electromagnetism |
| Applications | Electrical components such as inductors and transformers, and devices such as electric motors, generators, microphones, electric guitars, and induction cooktops |
| Induction | The current or voltage is called an induced current or an induced voltage |
| Inductance | When induction occurs in an electrical circuit and affects the flow of electricity |
| Eddy currents | Induced currents that flow in closed loops in planes perpendicular to the magnetic field |
| Self-inductance | The property of a circuit whereby a change in current causes a change in voltage in the same circuit |
| Mutual inductance | When one circuit induces current flow in a second nearby circuit |
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Electromagnetic induction
Faraday's law states that a voltage is induced in a circuit when there is relative motion between a conductor and a magnetic field. This means that either the magnetic field or the conductor can move, resulting in the production of an electromotive force (emf) or voltage. The magnitude of the induced voltage is directly proportional to the speed of movement. For example, when a bar magnet is moved through a coil of wire, the voltage detector in the circuit measures the induced voltage.
The discovery of electromagnetic induction led to a significant link between electricity and magnetism. It demonstrated that a changing electric current creates an associated changing magnetic field, which can then generate another changing electric current in a nearby conductor. This chain reaction is the reason behind the operation of many electrical devices.
James Clerk Maxwell mathematically described Faraday's discovery as Faraday's law of induction, which was later generalized into the Maxwell-Faraday equation, one of the four Maxwell equations in his theory of electromagnetism. Lenz's law, another fundamental principle in electromagnetic induction, determines the direction of the induced current and is derived from Faraday's law.
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Faraday's law
Induction, in relation to electricity, is the process by which an electrical conductor becomes electrified when near a charged body.
Michael Faraday is credited with the discovery of electromagnetic induction in 1831, and James Clerk Maxwell mathematically described it as Faraday's law of induction. Faraday's law was later generalized to become the Maxwell-Faraday equation, one of the four equations in Maxwell's theory of electromagnetism.
Faraday's experimental observations led to the conclusion that an EMF is induced when the magnetic flux across the coil changes over time. This change in flux produces a voltage across a coil.
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Electric generators
A basic electromagnetic generator consists of a stationary cylinder called a stator and a rotating shaft called a rotor. The stator is made up of insulated wire coils that generate a magnetic field, while the rotor turns within this field to produce electricity. As the rotor spins, it creates an electric current in each section of the wire coil, with each section acting as a separate electric conductor. These individual currents then combine to form a single large current, which is the electricity that is transmitted through power lines to consumers.
Generators can be driven by various sources of mechanical energy, including turbines, internal combustion engines, and renewable sources such as wind and water. Turbine generators, for example, use a moving fluid (such as water, steam, or gas) to spin the blades mounted on a rotor shaft, converting the mechanical energy of the rotor's rotation into electrical energy. Wind turbines work similarly, harnessing the power of the wind to rotate the blades and generate electricity.
Another type of generator is the alternator, which is often considered a type of generator but differs in its design and application. While generators feature a stationary magnetic field with a rotating armature, alternators have a rotating magnetic field with stationary conductors. Alternators are typically used for alternating current (AC) applications and are more commonly found in smaller load devices like automobiles.
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Transformers
A transformer comprises several key components, including the magnetic core and the windings. The windings are coils of wire that carry the electrical current. The magnetic core is typically made of ferromagnetic material, such as laminated silicon steel or ferrite, and it directs the magnetic flux generated by the windings. The primary winding is the coil that is connected to the source of electrical energy, and the secondary winding is the coil that receives the transferred energy.
When alternating current flows through the primary winding, it generates a time-varying magnetic field around it. This magnetic field induces a magnetic flux in the transformer's core, which, in turn, induces a varying electromotive force (EMF) or voltage in the secondary winding. The ratio of the windings determines the voltage conversion, allowing transformers to efficiently adjust voltage for safe and effective power distribution.
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Inductance
The electric current produces a magnetic field around the conductor. The magnetic field strength depends on the magnitude of the electric current, and therefore follows any changes in the magnitude of the current. The generated magnetic field follows any changes in the current, and from Faraday's law of induction, we know that changing the magnetic field induces an electromotive force (EMF) in the conductor. This induced voltage created by the changing current has the effect of opposing the change in current. This is stated by Lenz's law, and the voltage is called back EMF.
An electronic component designed to add inductance to a circuit is called an inductor. It typically consists of a coil or helix of wire. Inductors are used in many areas of electrical and electronic systems and circuits.
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Frequently asked questions
Electromagnetic induction is the production of an electromotive force (emf) across an electrical conductor in a changing magnetic field.
When a conductor is placed in a moving magnetic field or when a conductor is constantly moving in a stationary magnetic field, a current is produced because of voltage production (electromotive force). This current is called an induced current.
Michael Faraday is credited with discovering electromagnetic induction in 1831. He arranged a conducting wire attached to a device to measure the voltage across the circuit and moved a bar magnet through the coiling.
Electric generators, also called alternators, work on the principle of electromagnetic induction. Other everyday machines that use electromagnetic induction include electric motors, microphones, electric guitars, and transformers.
