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The unit Henry is used to measure electrical inductance in the International System of Units (SI). It is named after American physicist Joseph Henry, who discovered electromagnetic induction independently of and at the same time as Michael Faraday in England. One henry is the value of self-inductance in a closed circuit or coil in which one volt is produced by a variation of the inducing current of one ampere per second. Inductors are integral for the proper functioning of many electronic circuits and other appliances, such as power supply circuits, transformers, audio circuits, and radio circuits.
| Characteristics | Values |
|---|---|
| Unit of | Electrical inductance |
| Symbol | H |
| Named after | Joseph Henry |
| Self-inductance | One volt is produced by a variation of the inducing current of one ampere per second in a closed circuit or coil |
| Mutual inductance | An electromotive force of one volt is induced in one coil if the current in the other is changing at a rate of one ampere per second |
| Derived unit based on | Kilogram (kg), metre (m), second (s), and ampere (A) |
| Inductance of a coil depends on | Size, number of turns, and the permeability of the material within and surrounding the coil |
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What You'll Learn
- The Henry is the unit of electrical inductance in the International System of Units (SI)
- The unit is named after Joseph Henry, an American scientist who discovered electromagnetic induction
- A coil has a self-inductance of 1 Henry when 1 ampere flowing through it produces flux linkage of 1 weber turn
- The inductance of a coil depends on its size, the number of turns, and the permeability of the material within and surrounding it
- The unit can be expressed in combinations of SI units, e.g. H = kg*m^2/s^2*A^2
The Henry is the unit of electrical inductance in the International System of Units (SI)
The formula for this relationship is V*t = L*I, where V is the voltage, t is time in seconds, L is the inductance, and I is the current. This formula demonstrates that the inductance in henries is equal to the amount of flux linkage (in webers) per ampere of current flow.
The inductance of a coil depends on its size, the number of turns, and the permeability of the material within and surrounding the coil. The unit Henry is derived from four of the seven base SI units: kilogram (kg), metre (m), second (s), and ampere (A). The symbol for the unit Henry is the capital letter 'H'.
In practical applications, the inductance of a coil can vary from a few tens of microhenries, such as in a small air-core coil used for broadcast AM radio tuning, to hundreds of henries in a large motor winding with many turns around an iron core.
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The unit is named after Joseph Henry, an American scientist who discovered electromagnetic induction
The unit of electrical inductance in the International System of Units (SI) is named the Henry (H) after Joseph Henry, an American scientist. Born in Albany, New York, in 1797, Joseph Henry was one of the first great American scientists. He was a pioneer in electromagnetism and made important discoveries in the field of electricity, including self-induction, which is of primary importance in electronic circuitry.
Henry's interest in science was sparked at the age of sixteen when he read a book of lectures on scientific topics. In 1819, he entered The Albany Academy, where he received free tuition. Despite his family's financial struggles, he excelled in his studies and even began tutoring other students to support himself. Henry's natural scientific abilities became apparent during his time at the academy, and he frequently assisted his teachers in their lessons. He went on to become a professor at the academy, teaching mathematics and natural philosophy.
Outside of the classroom, Henry conducted much of his significant scientific work. He was particularly interested in electromagnetism and performed experiments with electromagnets. In 1829, he made important design improvements to electromagnets, pioneering the construction of strong, practical electromagnets. He also built one of the first electromagnetic motors, a simple contraption that possessed all the basic components found in modern motors. During his experiments, Henry discovered the property of inductance in electrical circuits.
Independently and at about the same time as Michael Faraday in England, Henry discovered electromagnetic induction. This discovery led to the unit of electrical inductance being named after him. One henry is defined as the inductance of a circuit with an induced voltage of one volt and an inducing current that changes one ampere per second. This discovery had a significant impact on the field of electricity and electronic circuitry.
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A coil has a self-inductance of 1 Henry when 1 ampere flowing through it produces flux linkage of 1 weber turn
The Henry is the derived unit of electrical inductance in the International System of Units (SI). It is named after Joseph Henry, an American scientist who discovered electromagnetic induction at the same time as Michael Faraday in England.
A coil with a self-inductance of 1 Henry will produce a flux linkage of 1 weber turn when 1 ampere of current flows through it. In other words, when a current of 1 ampere is flowing through a coil and a flux linkage of 1 weber turn is produced, that coil has a self-inductance of 1 Henry. This can be expressed as:
1 Henry = 1 Weber turn per Ampere
The inductance of a coil depends on its size, the number of turns, and the permeability of the material within and surrounding the coil. The number of turns within a coil is directly proportional to the coil's inductance. This means that increasing the number of turns or loops within a coil will increase its inductance.
The physical size of an inductance is also related to its current-carrying and voltage withstand ratings. A small air-core coil used for broadcast AM radio tuning might have an inductance of a few tens of microhenries, while a large motor winding with many turns around an iron core may have an inductance of hundreds of henries.
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The inductance of a coil depends on its size, the number of turns, and the permeability of the material within and surrounding it
The unit of electrical inductance in the International System of Units (SI) is the Henry, named after Joseph Henry, the American scientist who discovered electromagnetic induction. A Henry is defined as 1 volt produced across an inductor by 1 ampere of electric current changing per second.
The inductance of a coil is dependent on three main factors: its size, the number of turns, and the permeability of the material within and surrounding it. The more turns a coil has, the greater its inductance. This is because a coil with more turns generates a greater amount of magnetic field force for a given amount of coil current.
The size of the coil also matters; a larger area results in greater inductance, while a smaller area leads to less inductance. This is because a larger coil presents less opposition to the formation of magnetic field flux for a given amount of field force.
The permeability of the material within and surrounding the coil is another key factor. The greater the magnetic permeability of the core, the greater the inductance, and vice versa. This is because a material with higher permeability results in a greater magnetic field flux for a given amount of field force.
Inductance can be increased by placing a ferromagnetic material, such as iron, in the centre of the coil. This aligns the magnetic domains of the core, and the magnetic field of the core adds to that of the coil, increasing the flux through it. This is known as a ferromagnetic core inductor and can increase the inductance of a coil by thousands of times.
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The unit can be expressed in combinations of SI units, e.g. H = kg*m^2/s^2*A^2
The unit of electrical inductance in the International System of Units (SI) is the Henry, with the symbol 'H'. It is named after Joseph Henry, an American scientist who discovered electromagnetic induction. The Henry is a derived unit based on four of the seven SI base units: kilogram (kg), metre (m), second (s), and ampere (A).
The Henry can be expressed in combinations of SI units, as shown in the following equation:
H = kg*m^2/s^2*A^2
Where:
- H = Henry
- Kg = kilogram
- M = metre
- S = second
- A = ampere
This equation demonstrates the relationship between the Henry and the base SI units. By multiplying the base units of kilogram, metre, and square second, and dividing by the square of ampere, we obtain the Henry as the resulting unit.
The Henry is used to measure the inductance of an electric circuit. When an electric current of one ampere per second changes in a circuit, an inductance of one Henry will produce an electromotive force or voltage of one volt across the inductor. This relationship between current, inductance, and voltage is described by the formula:
V(t) = L * I(t)
Where:
- V(t) = voltage across the circuit
- I(t) = current through the circuit
- L = inductance of the circuit
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Frequently asked questions
The Henry is the unit of electrical inductance in the International System of Units (SI). It is named after Joseph Henry, the American scientist who discovered electromagnetic induction.
The formula for Henry is V*t = L*I, where V is the voltage, t is time, L is the inductance, and I is the current.
Henry is calculated as the amount of flux linkage (in Webers) per ampere of current flow.
The units of Henry are H = V.s/A, where V = volt, s = second, and A = ampere.
