BlogNCERTSelf and Mutual Inductance

Self and Mutual Inductance

What is Inductance?

Electrical conductors are inductors, which oppose changes in current flowing through them. The SI unit of inductance is Henry, and L is used to represent inductance.

Henry is outlined because the quantity of inductance needed to supply an emf of 1 V in an exceeding conductor once this change in the conductor is at the speed of 1 Ampere per second.

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    an electrical current flowing through a conductor creates a flux around it. The strength of the sector depends upon the magnitude of the current. The generated magnetic field follows any modifications within the current, and from Faraday’s law of induction, we all know that ever-changing flux induces an emf in the conductor. Considering this principle, inductance is outlined because of the quantitative relation of the evoked voltage to the speed of change of current inflicting it. The electronic element designed to feature inductance to a circuit is an inductor.

    Factors Affecting Inductance

    Inductance in a circuit is affected by the following factors:

    1. Number of Wire Turns in the Coil
      Inductance is more while the wide variety of turns of wire withinside the coil is more. More coils of wires suggest a more quantity of magnetic field force for a given quantity of coil current.
    2. Coil Area
      Inductance is proportional to the coil region. Greater the coil region, the more the inductance. Greater coil region provides much less opposition to the formation of magnetic field flux for a given quantity of field force
    3. Core Material
      Inductance increases as the magnetic permeability of the core increases.
    4. Inductance decreases as coil length increases. A coil with a shorter length has a greater inductance.

    Mutual Inductance

    Mutual inductance is the opposition to a change in current in one coil caused by the presence of another coil. , if a medium of relative permeability μr is present, the mutual inductance would be M =μr μ0 n1n2π r21 l, where r1 is the radius of the inner coil, n1 is the number of turns of the outer coil, and n2 is the number of turns per unit length of both coils.

    What is Self Inductance?

    Current carrying coils have the property of self-inductive resistance or opposition to the flow of current through them. This happens particularly because of the self-prompted emf produced withinside the coil itself. In easy terms, we also can say that self-inductance is a phenomenon in which there’s the induction of a voltage in a current-carrying wire.

    The self-prompted emf present withinside the coil will resist the upward thrust of current whilst the current will increase and it’s going to additionally resist the autumn of current if the current decreases. In essence, the route of the induced emf is contrary to the carried out voltage if the current is growing and the route of the triggered emf is withinside the equal course because the carried out voltage if the cutting-edge is falling.

    The above belongings of the coil exist most effective for the converting current that’s the alternating current and now no longer for the direct or consistent current. Self-inductance is usually opposing the converting current and is measured in Henry (SI unit).

    The induced current usually opposes the alternate in cutting-edge withinside the circuit, whether or not the alternate withinside the current is a boom or a decrease. Self-inductance is a kind of electromagnetic induction.

    Self-inductance Formula

    From Faraday’s law of electromagnetic induction, we can derive an expression for a coil’s self-inductance.

    VL = −N (dϕ / dt)


    VL = induced voltage in volts

    N = number of turns in the coil

    dφ / dt = rate of change of magnetic flux in webers / second

    An inductor’s induced voltage may also be expressed as the product of the current change rate and inductance (in henries).

    VL = −L (di / dt)


    E = −L (di / dt)

    Uses of Self Inductance

    Inductors store electrical energy in the form of magnetic fields. Typical applications include:

    1. Tuning circuits
    2. Sensors
    3. Store energy in a device
    4. Induction motors
    5. Transformers
    6. Filters
    7. Chokes
    8. Ferrite beads
    9. Inductors used as relays

    When current passes on a wire, and particularly when it passes through a coil or electrical device, flux is induced. This extends outward from the wire or inductor and will couple with different circuits. However, it additionally couples with the circuit from that it’s set up. The magnetic field will be envisaged as coaxial loops of magnetic flux that surround the wire, and bigger ones that link up with others from other loops of the coil enabling self-coupling within the coil. once this within the coil changes, this causes a voltage to be induced in the different loops of the coil – the results of self-inductance.

    Also read: Lenz’s Law: Formula, Definition, and Statement


    What is the difference between mutual and self-inductance?

    Self-inductance is the ability of a single isolated coil to produce emf depending on changes in magnetic flux. An induced emf is the result of induced inductance at a pair of coils when the magnetic flux of one coil is coupled to the magnetic flux of the adjacent coil.

    What is the S.I unit of self-inductance?

    Weber/ampere or volt-second/ampere is the SI unit of self-inductance. Henry (H) is another name for it.

    3. What are the factors that affect mutual inductance?

    Ans: Mutual inductance between two coils is affected by;

    • Area of cross-section
    • Number of turns in each coil
    • Space between the two coils
    • Permeability of medium between the two coils
    • Length (in case of the solenoid)
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