What is Self Inductance : Theory, Factors & Its ApplicationsIn any circuit, when the switch is closed, the source of emf like the battery will start pushing the electrons in the whole circuit. So the flow of current will be increased to create the magnetic flux using the circuit. This flux will create an induced emf within the circuit to generate a flux to restrict the increasing flux. The induced emf direction is opposite to the battery so the flow of current will be increased gradually rather than an instantaneous one. This induced emf is known as self-inductance otherwise back emf. This article discusses an overview of self-inductance.What is Self Inductance?Definition: When the current-carrying coil has the property of self-inductance, then it resists the change in the current flow is known as self-inductance. This mainly occurs when the self-induced e.m.f is generated within the coil. In other words, it can be defined as when the voltage induction occurs within a current-carrying wire. Self InductanceWhen the current increases or decreases, the self-induced e.m.f will resist the current. Basically, the path of the induced e.m.f is reverse to the voltage applied, if the current is rising. Similarly, the path of the induced e.m.f is in a similar direction to the applied voltage, if the flow of current is reducing,The above coil property mainly occurs when the flow of current changes which is the AC but not for the steady current or DC. Self-inductance resists the flow of current always, so it is a kind of electromagnetic induction and the SI unit of self-inductance is Henry.Self Inductance TheoryOnce the current flow throughout a coil, then a magnetic field can be induced, so this extends externally from the wire and this can be connected through other circuits. The magnetic field can be imagined like concentric loops of magnetic flux that enclose the wire. The larger ones connect through others from the additional loops of the coil that enables self-coupling in the coil.Self Inductance WorkingOnce the flow of current within the coil alters, then the voltage can be induced various loops of the coil.In terms of quantifying the effect of the inductance, the basic Self Inductance formula below quantifies the effect.VL=−Ndϕdt From the above equation,‘VL’ is an induced voltage‘N’ is the no. of turns within the coil‘dφ/dt’ is the magnetic flux rate of change within Webers / SecondThe voltage which is induced within an inductor can also be derived in terms of the inductance & the rate of current change.VL= −LdidtSelf-induction is one type of method which operates the single coils as well as chokes. A choke is applicable in RF circuits as it resists the RF signal and allows Dc or steady current to supply.DimensionThe unit of self-inductance is H (Henry), so the dimension of self-inductance is ML2T -2A-2Where ‘A’ is the cross-section area of the coilThe induced e.m.f production within a circuit can occur because the modify within a magnetic flux in its adjacent circuit is known as mutual induction.We know that E = ½ LI2From the above equation, L = 2E/I2L = E/I2= ML2T-2/A2 = ML2T-2A-2The Relation between Self Inductance and Mutual InductanceAssume the no. of coils in the primary winding is ‘N1’, the length is ‘L’ and the cross-section area is ‘A’. Once the flow of current through this is ‘I’, then the flux connected to it can beΦ = Magnetic Field * Effective AreaΦ = μoN1I/l × N1AThe primary coil’s self-inductance can be derived asL1= ϕ1/IL1=μN12A/l Likewise, for the secondary coilL2 = μN22A/lOnce the current ‘I’ supplies throughout ‘P’, then the flux connected coil ‘S’ isϕs = (μoN1I/l)×N2ATwo coils mutual inductance isM = ϕs/IFrom both the equations od√L1L2 = μoN1N2A/lBy contrasting this through mutual inductance method we can getM = √L1L2FactorsThere are different factors affecting the self-inductance coil that includes the following.Turns in the coilInductor coil areaCoil lengthThe material of the coilTurns in the CoilThe coil’s inductance mainly depends on the turns of the coil. So they are proportional with each other like N ∝ L The inductance value is high when the turns within the coil are high. Similarly, the inductance value is low when the turns within the coil are low.Inductor Coil AreaOnce the area of the inductor increases then the coil’s inductance will be increased (L∝ N). If the coil area is high, then it generates no. of magnetic flux lines, so magnetic flux can be formed. Therefore the inductance is high.Coil LengthWhen the magnetic flux induced in a long coil, then it is less than the flux induced within a short coil. When the magnetic flux which is induced is reduced, then the coil’s inductance will be reduced. So the coil induction is inversely proportional to the coil’s inductance (L∝ 1/l)The Material of the CoilThe material’s permeability with the wrapped coil will have an effect on the inductance and induced e. m.f. The high permeability materials can generate less inductance.L ∝ μ0.We know μ = μ0μr, then L∝ 1 / μrExample of Self InductanceConsider an inductor including copper wire with 500 turns, and it generates 10 milli Wb of the magnetic flux once 10 amps of DC current flow through it. Calculate the self-inductance of the wire.By using the main relation of L & I, the inductance of the coil can be determined.L = (N Φ)/IGiven that, N = 500 turnsΦ = 10 mille Weber = 0.001 Wb.I = 10 ampsSo inductance L = (500 x 0.01) / 10= 500 Milli HenryApplicationsThe applications of self-inductance include the following.Tuning circuitsInductors used as relaysSensorsFerrite beadsStore energy in a deviceChokesInduction motorsFiltersTransformersThus, this is all about an overview of self-inductance. When the flow of current within the coil changes then the flux linked through the coil will also be changed. Under these conditions, an induced emf can be generated in the coil. So this emf is known as self-induction. Here is a question for you, what is the difference between mutual and self-inductance? Share This Post: Facebook Twitter Google+ LinkedIn Pinterest Post navigation ‹ Previous What is a Flux Meter : Working & Its ApplicationsNext › What is a Clamp Meter : Construction & Its Working Related Content What is a Sampling Oscilloscope & Its Working What is a Shunt Reactor : Construction & Its Working What is a Shunt Capacitor & Its Working What is a Savonius Wind Turbine : Design & Its WorkingAdd Comment Cancel replyComment:Name * Email * Website