Inductance of an Indcutor

Inductance of an Indcutor
Inductance of an Indcutor

Inductance is essential to electronics and electrical engineering. This study examines inductor inductance. Electronic circuits require understanding inductors’ behavior to design and analyze them. This study will explain inductance in circuits and its uses. Inductance factors, calculation methodologies, and common inductor applications will also be covered.

The inductor stores and releases energy as an electromagnetic field. Electronic circuits employ inductors to manage current and energy conversion. They can store energy and smooth current and voltage variations. Transformers, motors, and generators use inductors to efficiently transport and transform electrical energy. Understanding an inductor’s role optimizes circuit performance and ensures functionality.

Inductance Definition 

Inductance measures an inductor’s ability to store energy in a magnetic field as current passes through it. It is the ratio of the induced electromotive force (emf) to the inductor’s current change. The SI unit of inductance is the henry (H), named after electromagnetic researcher Joseph Henry. Inductance measures an inductor’s resistance to current flow and calculates its magnetic flux output per current. Analyzing and developing electronic circuit inductors requires understanding inductance.

Circuit Inductance Importance

Due to its effects and applications, inductance is crucial to circuits. First, inductance stores energy in a magnetic field to control current and voltage. Power supplies are stabilized and noise-filtered by inductors. Inductance also allows electronic circuits to create oscillators for precise timing signals. Filters employ inductors to pass or block frequencies for signal processing. Inductance in circuits is crucial to many applications and electronic devices.

Like capacitors and resistors, inductors are passive. An inductor is a twisted wire or coil of electroconductive material. An electric conductor or circuit with inductance resists current flow.An inductor is an electric conductor or circuit element with inductance. A coil or twisted wire (inductor) generates an electromotive force (EMF) in itself and surrounding conducting materials to counteract a current change.Capacitance measures a conductor’s ability to store electric field energy. In contrast, an electrical conductor’s inductance measures its magnetic charge storage (magnetic field energy).

An inductor stores energy as magnetic field. Inductance is connected with current-carrying material because magnetic field is associated with current flow. A coil’s inductance is proportional to its turns.Dielectric materials like plastic, wood, and glass have low inductance. Ferro magnetic materials (iron, Alnico, chromium ferroxide) have high inductance.

Self Inductance

A current carrying conductor’s inductance or self-inductance induces an EMF when current flow changes.An alternating changing current across the inductor coil changes its magnetic flux, causing the induced emf. This is called “Self induction” and the coil’s inductance is called “Self-inductance”.Self inductance is explained by a current-carrying circuit element or N-turn inductor coil. When current runs through the coil, a magnetic field is created and released.

Due to this magnetic field, magnetic flux is introduced. Thus, coil self-inductance is magnetic flux linkage per current. Self-emf is induced in the inductor coil when it intercepts electric field-driven magnetic flux lines.A coil’s self-inductance is its capacity to resist current change. Measured in Henry. Coil self-inductance depends on its magnetic characteristics.This is why ferromagnetic materials enhance coil inductance by increasing magnetic flux.

The formula for coil self-inductance is

  • L = N Φ /I
  • Where N is the coil’s turns.
  • Φ represents magnetic flux.
  • Current owing to emf production is I.
  • Henries inductance is L.

Self Induced EMF and Coefficient of Self Inductance

Current flow via an inductor is denoted by I, while magnetic flux is Φ. Both are proportionate. It can be represented as I ∝ Φ.Turns in the inductor are proportional to coil current. Current and induced emf are related as follows.

  • (dΦ)/dt = L (di)/dt

Coil geometry determines inductance. Its value is called “coefficient of self-inductance”.

  • e = – (dΦ )/dt
  • –L (di)/dt

Using high or low permeability materials and coils with variable turns, we can construct inductor coils to our needs. The magnetic flux inside an inductor core is

  • Φ = B x A

B is flux density and A is coil area.

Self-inductance in a long solenoid

A long hollow solenoid with cross sectional area A, length l, and n turns has a magnetic field due to current I as follows.

  • B=μ0 H=μ0(N.I)/l
  • The total flux in the solenoid is N Φ = LI.
  • In the equation, substitute this.
  • L = N Φ /I
  • L = (μ0 N2 A )/ l
  • Henry self-inductance is L.
  • The permeability of air or hollow space is μ0.
  • N is the inductor’s coil turns.
  • Solenoid inner cross sectional area is A.
  • l is coil length in meters.

Long hollow solenoid self-inductance. The solenoid material’s absolute permeability is μ. We calculated the self-inductance of the hollow solenoid using μ0.Soft iron fills the solenoid for high permeability and magnetic flux.

Self Inductance of a circular coil

Find the self-inductance of a circular inductor. Consider a circular coil with A = π r2 cross section and N turns. The magnetic flux is then

  • B = μ0 (N.I )/2r
  • The total flux in a circular conductor is N Φ = LI.
  • In the equation, substitute this.
  • L = N Φ /I
  • L = (μ_0 N2 A )/2r
  • Since the area of a circle is A = π r2, the self-inductance of a circular inductor is also given as
  • L = (μ0 N‍2 π r )/2

Factors Affecting the Self Inductance

Observing the above equation of inductance, we can say there are 4 factors that affect the self-inductance of a coil, they are

  1. Number of turns in the coil (N)
  2. Area of the inductor coil (A)
  3. Length of the coil (l)
  4. Material of the coil

Number of turns

Coil inductance depends on its turns. The number of coil twists and inductance are related. N ∝ L

  • More turns increase inductance.
  • Lower turns reduce inductance.

Crosssectional area

Coil inductance increases with inductor cross sectional area. L∝ N. High coil area produces more magnetic flux lines and magnetic flux. The inductance will be high.

Coil length

Longer coils create less magnetic flux than shorter coils. As generated magnetic flux diminishes, coil inductance falls. So coil induction is inversely proportional to inductance. L∝ 1/l

Material of the coil

The permeability of the material with which the coil is wrapped, will have an effect on the induced emf and inductance. The materials with high permeability can produce low inductance.


We know μ = μ0 μr

So L∝ 1 / μr

Mutual Inductance

Mutual induction occurs when a coil’s current flow changes due to its connected or adjacent coil. The same magnetic field affects both coils.As detailed in the self-inductance notion, Faraday’s law and Lenz’s law explain mutual inductance’s emf and direction.

Emf always opposes magnetic field change. The first coil’s current change produces second coil emf.Second coil induced EMF2 = -N2 A ΔB/Δt – M (ΔI1)/Δt.The mutual inductance (M) is proportional to the second coil’s emf and the first coil’s current change.

Mutual Inductance

The graphic above explains mutual inductance. Twisted two inductors around one conductor. Call them loops 1 and 2. Changes in loop 1 current cause magnetic flux.Loop 2 intercepts magnetic flux without current entering the second coil, causing EMF. This is mutual induction.

Mutual Induction EMF and Coefficient

Keeping the 2 coils in the current-varying field induces an emf due to current flow. Magnetic flux varies with loop current.Mutual induction is a vector quantity because it can induce in 2nd coil owing to 1st coil current flow or in 1st coil due to 2nd coil magnetic flux (B).

Be the first to comment

Leave a Reply

Your email address will not be published.