How Is the SI Unit of Inductance Used in Physics?
The attribute of a current-carrying closed-loop that causes an electromotive force to be generated or induced by a change in the current flowing via it. Such an attribute is called the inductance.
On This Page, We'll Learn About the Following:
Inductor unit
Inductance unit
S.I. unit of inductance
What is the si unit of inductance?
Inductor
An inductor is a coil of wire cloaked around a magnetic material.
Current flowing via the inductor generates a magnetic field that does not change, as it is trying to oppose the change in the flow of current which means the current flow remains constant inside the inductor.
The inductor won’t generate any forces on the charged particles flowing via it. In such a case, the inductor just behaves like a normal wire.
The current flow is opposed by the resistance, and the time comes when there comes a
current decay (decline). The larger the resistance, the faster the current will decline.
On the other hand, the larger the inductance of the inductor, the slower the current will decay.
What is Inductance?
The inductance is the ability of an inductor or any current-carrying conductor to oppose the change in the current flowing through it. The inductors do this by generating a self-induced emf within itself (Faraday’s law of induction) as a result of their changing magnetic field.
S.I. Unit of the Inductor
The S.I unit of the inductor is Henry H
MKS unit is Kg m² s⁻² A⁻²
Where one Henry is equal to the one-kilogram meter squared per second squared per ampere squared.
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What is Self - Inductance?
Inductance is also called self-inductance. When a current is established in a closed conducting loop, it creates a magnetic field. This magnetic field has flux produced in an area of the closed-loop. If the current varies with time, the flux via the loop also changes. Hence an EMF is induced in the loop. Such a process is called self-induction.
The magnetic field at any point due to current is proportional to the current. The magnetic flux in an enclosed area of the conductor can be represented as,
φ ∝ i ⇒ φ = L i
Where L is a proportionality constant and is called the coefficient of self-inductance or simply self-inductance of the loop.
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The inductance in the coil (Fig.1) depends on the number of turns, area of cross-section, and nature of the material of the core on which the coil is wrapped.
If i =1, φ = L x i or L = φ
Therefore, the coefficient of self-inductance is numerically equal to the amount of magnetic flux linked with the coil when unit current flows through the coil.
From Faraday’s law of induction, any variation in the magnetic field generates emf, given by,
E = - dφ (t) / dt = - L di / dt
The negative sign indicates that the changing current induces a voltage in the conductor and this induced voltage is in a direction that tends to oppose the change (increase or decrease) in the electric current (Lenz’s law) is called the back EMF.
Inductance for a Long Solenoid
The inductance of a solenoid is given by,
B = μ₀ N I / L
The magnetic flux density can be obtained by multiplying the B with cross-sectional area A, we get,
φ = B xA = μ₀ N x i x A / l….(1)
Since total magnetic flux inside the coil = flux via each turn x total number of turns.
φ = B xA = μ₀ N x N i x A / l….(2)
Where μ₀ is the magnetic constant or absolute magnetic permeability of free space/air forms the core of the solenoid.
N = The total no of turns of the solenoid
i = The current
l = The length of the solenoid
A = Area of each turn of the long solenoid
We know that
φ = L i….(3)
From (2) and (3) we get,
L i = μ₀ N x N x A xi / l x N we get,
L = μ₀ N² x A/ l
μ = μ₀ . μr
When the core is of any other magnetic material μ₀ is replaced by
μr (relative magnetic permeability).
Here, we Conclude the Following Things,
L increases with the number of turns in the coil.
It depends on the magnetic permeability of the material.
The cross-sectional area.
L is independent of the current.
S.I. Unit of Inductance
The S.I. unit of self-inductance is weber/ ampere or volt-second/ ampere.
It is also denoted by Henry (H), named after an American scientist named Joseph Henry.
Where Henry is the amount of inductance that generates a change of one volt and when the current is varying at the rate of one ampere per second.
Note: All conductors have some inductance, which may have either desirable or detrimental effects in electrical circuits and it depends on the geometry of the current path and on the magnetic permeability of the materials.
The ferromagnetic material tends to have a high inductance because of the flow of large amounts of electric flux (total magnetic field) through the conductor produced by a current flowing through it increases the inductance in that conductor.
Inductor Working Principle
When ac current is applied to the inductor coil, its own current changes, causing its own magnet to change, creating an electromotive power. This condition is called self-inductance. The direction of the self-induced current is always affected. When the alternating current increases, the direction of the self-inductance current is opposite to that of the AC current. When the AC current is weak, the direction of the self-inductance current is the same as that of the alternating current, which has a blocking effect.
Self-Induction- When the current flows into the coil, a magnetic field is produced around the coil. As the current in the coil changes, the surrounding magnetic field also changes accordingly. This change in a magnetic field can cause the coil itself to generate electromotive energy (EMF is used to represent the terminal voltage of the active power of the active components).
Mutual Inductance- If two coils of an inductor are close together, the magnetic field conversion of one coil will affect the other, and this effect is mutually beneficial. Its size depends on the degree of interaction between self-inductance and the two coils. The components formed by this policy are called mutual inductors.
Factors affecting Inductance in a Circuit
The following factors affect inductance in a circuit
The Number of Wires Transforming into Coil - The greater the amount of cable twist on the coil, the greater the inductance. Slight twisting of the cable to the coil results in a small inlet. Most cable coils show a large amount of magnetic field in a given number of current coils.
Coil Location - The larger the coil area, the greater the inductance. The location of the small coil leads to the small entrance. The large coil area exhibits minimal resistance to the formation of magnetic field flux, with a given amount of field strength
Material of the Coil - The greater the magnetic field of the core where the coil is wrapped, the greater the reach; less contextual access reduced inductance.
Length of the Coil - When the coil length is longer, the inductance decreases. The shorter the coil length, the greater the inductance.
Summary
With the change in the magnetic flux, induced emf is a must, but induced current will only appear only when the circuit is closed.
An Inductor is equivalent to a short circuit to DC, because once the storage phase has been completed, the current, i, that flows through is stable, no emf is induced. So the inductor behaves like a normal wire where Resistance R is zero
FAQs on SI Unit of Inductance: Definition, Symbol & Importance
1. What is inductance and how is it defined in Physics?
Inductance is the fundamental property of an electrical conductor where a change in the current flowing through it induces an electromotive force (EMF). This phenomenon occurs in the conductor itself (self-inductance) and in any nearby conductors (mutual inductance). It is formally defined as the ratio of the induced voltage to the rate of change of current causing it. Essentially, inductance measures an inductor's opposition to any change in the electric current.
2. What is the SI unit of inductance and its official symbol?
The SI unit of inductance is the Henry, named in honour of the American scientist Joseph Henry. The official symbol for this unit is H. A circuit is said to have an inductance of one Henry if a current changing at a rate of one ampere per second produces an electromotive force of one volt across it.
3. What is the difference between an inductor and inductance?
While related, these terms are distinct. Inductance (L) refers to the physical property or characteristic of opposing a change in current. An inductor is the actual electronic component, typically a coil of wire, that is designed to provide a specific amount of inductance in a circuit. In short, an inductor is the device that possesses the property of inductance.
4. What is the importance of inductance in real-world applications?
Inductance is vital in modern electronics due to its ability to store energy in a magnetic field and react to changes in current. Key applications include:
- Filtering: Inductors, often called chokes, are used to block high-frequency AC noise in power supplies while allowing DC signals to pass.
- Tuning Circuits: Combined with capacitors, inductors form LC circuits that are essential for selecting specific frequencies in radio and TV receivers.
- Transformers: The principle of mutual inductance is the basis for all transformers, which are crucial for stepping up or stepping down voltage levels in power distribution systems.
- Energy Storage: In devices like switch-mode power supplies, inductors temporarily store and release energy to regulate voltage efficiently.
5. What key factors determine the inductance of a coil?
The inductance of a coil is determined by its physical characteristics rather than being an intrinsic material property. The primary factors are:
- Number of Turns: Inductance is proportional to the square of the number of turns in the coil.
- Core Material: The material within the coil (the core) has a major impact. A core made of a ferromagnetic material (like iron) significantly increases inductance compared to an air core due to its higher magnetic permeability.
- Coil Geometry: The cross-sectional area and the length of the coil also affect its inductance. A larger area increases inductance, while a greater length (for the same number of turns) decreases it.
6. Why does an inductor seem to block AC but allow DC to pass easily?
This behaviour is rooted in an inductor's opposition to *change* in current. For a Direct Current (DC), the flow is steady and constant, so there is no change for the inductor to oppose. It acts like a simple wire with low resistance. For an Alternating Current (AC), the flow is constantly changing direction and magnitude. The inductor continuously opposes these changes by generating a back EMF. This opposition, known as inductive reactance (Xₗ), increases with the frequency of the AC, effectively blocking high-frequency currents.
7. How can the Henry (H) be expressed in terms of other SI units?
The Henry (H) is a derived SI unit. It can be expressed using other units to understand its physical meaning. One Henry is equivalent to:
- One Volt-second per Ampere (V·s/A)
- One Weber per Ampere (Wb/A)
When broken down into fundamental SI base units, one Henry is equal to kilogram metre squared per second squared per ampere squared (kg·m²/s²·A²).
8. What is the difference between self-inductance and mutual inductance?
Both are forms of inductance but describe different interactions:
- Self-Inductance (L) describes the phenomenon where a changing current in a coil induces a voltage (back EMF) within that *same coil*. It is the coil's inherent tendency to resist changes in its own current.
- Mutual Inductance (M) describes the effect where a changing current in one coil induces a voltage in a *separate, nearby coil*. This occurs because the magnetic field from the first coil couples with the second. This is the core principle of transformers.
9. How is the energy stored in an inductor related to its inductance?
An inductor stores potential energy within the magnetic field generated by the current flowing through it. The amount of stored energy (U) is directly proportional to both the inductance (L) and the square of the current (I). The relationship is given by the formula U = ½LI². This means that an inductor with a higher inductance value or one carrying a greater current will store more energy. This energy is released back into the circuit if the current decreases or is interrupted.
