What is Inductance: Definition and 494 Discussions

Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The flow of electric current creates a magnetic field around the conductor. The field strength depends on the magnitude of the current, and follows any changes in current. From Faraday's law of induction, any change in magnetic field through a circuit induces an electromotive force (EMF) (voltage) in the conductors, a process known as electromagnetic induction. This induced voltage created by the changing current has the effect of opposing the change in current. This is stated by Lenz's law, and the voltage is called back EMF.
Inductance is defined as the ratio of the induced voltage to the rate of change of current causing it. It is a proportionality factor that depends on the geometry of circuit conductors and the magnetic permeability of nearby materials. An electronic component designed to add inductance to a circuit is called an inductor. It typically consists of a coil or helix of wire.
The term inductance was coined by Oliver Heaviside in 1886. It is customary to use the symbol



L


{\displaystyle L}
for inductance, in honour of the physicist Heinrich Lenz. In the SI system, the unit of inductance is the henry (H), which is the amount of inductance that causes a voltage of one volt, when the current is changing at a rate of one ampere per second. It is named for Joseph Henry, who discovered inductance independently of Faraday.

View More On Wikipedia.org
Recent contents Top users
  1. M

    Engineering How to find the inductance of this circuit

    I got stuck doing this question. Please correct my mistakes and help me out. 1. The angular frequency ω is FIXED to 2 [rad/s] whereas the inductance L is changeable. When L=1/8, resonance occurs in the circuit and the magnitude of current i reaches its minimum value. From this state, L is...
  2. R

    Equivalent Inductance: Redrawing Circuits and Solving for Leq

    Homework Statement Homework Equations Leq = L1 + L2 + ... + Ln (series) Leq = 1/((1/L1) + (1/L2) + ... + (1/Ln)) (parallel) The Attempt at a Solution For part A, I redrew the circuit (above), taking into account that the switch was open, but I'm not entirely certain I did it...
  3. Gliese123

    Formula/calculation of the magnetic field & inductance in a AC cable

    Hello dear PF-members! :shy: I'm looking for some appropriate formula which could be utilized to calculate the magnetic field density in a straight high voltage AC mere cable. If you're more into the details of why I may ask this - I'm working with the railway maintenance and got interested in...
  4. S

    Find the mutual inductance between the coil and the wire in two ways

    Homework Statement We have a toroidal coil, and an infinite wire that runs through it on its symmetry axis. (See picture) We need to find the mutual inductance between the coil and the wire in two ways: 1. By running a current through the wire, and finding the induced voltage in the...
  5. A

    Average power to ZL coupling coefficent and mutual inductance M?

    Homework Statement In the circuit of Figure 4-2, let N1=2000 turns, N2=1000 turns, R=0, Z1=0 and ZL=300+j400 (Ω). If V1(max)=1500 V, what is the average power delivered to ZL? A. 5400 W B. 2700 W C. 337.5 W D. 675 WHomework Equations V2=(N2/N1)V1The Attempt at a Solution since turn factor is...
  6. ShreyasR

    Understanding mutual inductance

    In mutual inductance, energy transfer takes place from one circuit to another through magnetic flux. But while trying to understand the equations involved from the attached image, I am getting confused. If the current in the first coil gives rise to a flux \phi1 and only a part of it (\phi12)...
  7. ShreyasR

    Understanding inductance coil.

    I know that an inductor opposes a change in current through it. So in the circuit diagram attachment, When the switch is closed, current starts increasing in the circuit and reaches a maximum value. And When in steady state, if the switch is suddenly turned off, The inductor opposes the sudden...
  8. A

    Mutual inductance between straight line cable & square shape Frame

    Homework Statement Calculate mutual-inductance between straight line cable and square shape frame, as shown on picture. Homework Equations I am not sure which equation will be used here because as far as my knowledge goes , mutual inductance should be concerned with turns in...
  9. A

    Inductance of Solenoid on Coaxial Cable

    Homework Statement The figure below shows a short coil which is coaxial with a very long solenoid (you may approximate it as infinite.) Coil: Has 120 turns of radius 1.8 cm and resistance 5.8 . It is not attached to anything. Solenoid: Has 22700 turns/m and a radius of 1.6 cm. It receives an...
  10. T

    Physical Quantity Analogous to Inductance

    Hi, I understand that some physical quantities in electromagnetism are analogous to physical quantities in heat transfer. For instance, electric field is analogous to temperature gradient. I want to know which physical quantity in heat transfer is analogous to Inductance ("L") ...
  11. D

    Mutual Inductance Homework Solution

    Homework Statement Derive an expression for the mutual inductance ,L12, for the case of the figure, assuming a current distribution: J_{2}(x)= F_{2}(x), h1<x<h2 or I_{2}(x)= ∫^{h_2}_{h_1} F_{2}(x)w_{2}dxHomework Equations L_{12}(x)=∅_{12}(x)/ i_{2}(x) The Attempt at a Solution In fact I don't...
  12. A

    Are My Calculations on Coils and Inductance Correct?

    Hi there I needed someone to check my answers for these questions and see if they are correct and if not if they can point me in the right direction the question is for revision purposes got an exam in a week. Thanks. A coil of inductance 4H and resistance of 80Ω is connected in parallel...
  13. AJKing

    Inductance and Magnetic Energy of a Straight Wire

    Homework Statement A long wire carries a current i uniformly distributed over a cross section of the wire. Show that the magnetic energy of a length l equals μ_0 i2 l / 16π. Describe why this doesn't depend on diameter. Show that the inductance for a length of the wire l associated with the...
  14. B

    Solving for AC Voltmeters with a Pure Resistance and Pure Inductance

    Homework Statement a) A pure resistance and a pure inductance are connected in series across a 100 V(rms) AC line. An AC voltmeter gives the same reading when connected across either the R or the L. What does it read? (Note: Meters read rms values.) b) The magnitudes of R and L are...
  15. M

    Calculate the inductance of a coil of wire

    Homework Statement Calculate the inductance (SI units: Henries) of a coil of wire having a loop diameter of 0.5 cm and coil length of 10 cm. The wire has 1000 loops per meter. Homework Equations I think I can use this equation: L= μₒAN² / x, x = length of wire, μₒ = 4π*10^-7 Tm/A A...
  16. U

    Mutual Inductance of coaxial coils

    Homework Statement Not sure if I'm correct or wrong..because usually M12 = M21 The Attempt at a Solution Here coil 1 and coil 2 are coaxial, with coil 2 being shorter and having smaller area.
  17. E

    Voltmeter in Series as self inductance of cables is significant

    Hello, I am using a lock-in amplifier to measure the AC voltage across a small sample of superconducting wire located in a cryostat. As the self-inductance and the capacitance of the wires used for the measurement are non-negligible, I have basically connected the lock-in amplifier in series...
  18. S

    Mutual Inductance Between Square and Circle Circuit

    Homework Statement There are two circuits in the XY plane: one is a square (side 0.2 m in length) centered on the origin. The second is circle or radius r also centered on the origin. The circle is smaller than fits inside) the square. By assuming the radius of the circle is small compared...
  19. V

    Trying to emulate Inductance with gyrator

    Hello All, I am working on a project where I am trying to replicate the behavior of a particular inductance module used on an automobile. It is a simple component that receives a signal from a control unit and the response is sent back via ground. The attached PNG file shows the setup, it is...
  20. J

    Inductance of hollow conductor (copper pipe)

    Hi Everyone, I'm working on some inductance calculations and was wondering if anyone knows of any formulas (or methods) to determine the inductance of a straight piece of copper pipe, if the ID, wall thickness, and length are known? The closest thing I have found so far was the inductance of...
  21. H

    Calculating leakage inductance & winding capacitance of a step up transformer?

    I am designing a small step up transformer and I'm trying to calculate leakage inductance and winding capacitance. The problem I'm having is when I search the web I find there is a ton of info on the subject. So I have no idea where to start. Can anyone explain to me how to calculate...
  22. J

    How Does Inductance Affect DC Circuit Behavior?

    1. An inductor of negligible resistance and an inductance of 0.2 H is connected in series with a 330 Ω resistor to a 12V d.c. supply. Determine: (a) the time constant of the circuit (b) the voltage drop across the inductor after two time constants (c) the voltage drop across the...
  23. B

    Circuit with two resistances and inductance

    Homework Statement http://img534.imageshack.us/img534/5788/gimpjl.png I have this circuit and I want to know i_1 and i_2 (currents in R_1 and R_2). \varepsilon is electromotive force and L is inductance. I'd like to know if the following system of equations is correct and if I can get i_1...
  24. W

    Mutual inductance of transformer with coils of different area and length

    Hello, I am trying to derive the mutual inductance between the two coils of a transformer. I want to do this for two coils with different lengths and different cross-sectional areas (assuming that one side of the transformer core is thicker than the other). The parameters are therefore: I1...
  25. C

    Inductance of VR crank sensor

    I helped my colleagues simulate inductance of vr crank sensor in Maxwell but my simulation result is quite different compared to the test one. Our sensor is quite simple, just a piece of permenant magnet, a piece of flux concentrator made of normal steel, and one copper coil hooked outside of...
  26. S

    Calculating Resistance and Inductance of Coil in AC Circuit

    1. Homework Statement . A wire coil has both resistance and inductance, and is connected in series to an AC power supply with 80Hz and 180V, drawing 0.4A current and 18W power. The circuit consists of a single loop. 1. Calculate the inductance and resistance of coil 2. Plot vector of...
  27. A

    How to Determine Inductance in RL Circuits for a Required Current Response Time?

    Homework Statement An inductor is connected in series with a 1000 ohm resistor and a battery. What mus be the inductance in millihenries of the inductor if the current in the circuit is required to reach 90% of its final value after 20 microseconds? Homework Equations I am not actually...
  28. G

    Induction Coil Failure with increaseing inductance as coil is unwound

    I have a 13 layer 130mH induction coil that failed and now registers 6.64mH. During the failure analysis the coil was unwound layer by layer and the induction dropped in steps of 0.7-1.5mH to a value of 1.3mH until the 8th layer was removed the the inductance increased to 5.4mH. Then the 9th...
  29. J

    How to find inductance of a coil with two concentric ferromagnetic cores?

    Homework Statement This isn't exactly a homework question so there aren't any data/numbers to work with. I just want to know what to do if there are two ferromagnetic cores inside a coil of wire, arranged as concentric cylinders. Or how to account for the air gap between the core and the coil...
  30. J

    Calculating the equivalent inductance of a simulated inductor

    Homework Statement I am asked to find the equivalent resistance of a simulated inductor shown above. We are told not to worry about the simulated inductor circuit. The simulated inductor will be incorporated into a larger circuit as shown below. 2. The attempt at a solution I am really...
  31. E

    Inductance of a coil (negative inductance?)

    Hi everyone, I encountered a problem as a part of the solution of which I needed to get the i-V relation across a solenoid to gain some intution in the other parts of the problem, which is the well known expression VL=LdiL/dt, where V and i are referenced with respect to the passive sign...
  32. P

    Find the inductance and capacitance of an RLC/LC circuit

    Homework Statement The energy of the RLC circuit decreases by 1% during each oscillation when R=2 Ohms. If this resistance is removed, the resulting LC circuit oscillates at a frequency of 1 kHz. Find the inductance and the capacitance. Hint: be aware of the difference between regular and...
  33. P

    Find the resistance and inductance ensuing a short-circuit

    Homework Statement To measure the inductance and resistance of a real inductor, a physicist first connects the inductor to a 3V battery. At these conditions, the final, steady, current is 24 A. Then the physicist suddenly short-circuits the inductor with a thick (resistance-less) wire place...
  34. R

    Archived Single phase question regarding Inductance

    Hi There, i have the following question. Can anybody start me off and hopefully i can finish it. Question; Two similar coils have a coupling coefficient of 0.6. Each coil has a resistance of 8 Ω, and a self-inductance of 2 mH. Calculate the current and the power factor of the circuit when...
  35. R

    Calculate Equivalent Inductance of Coils Connected in Series

    Homework Statement There are two coils wined around the same closed iron core. Their inductances on this iron core are measured to be 4 henry, and 9 henry. Then the two coils are connected in series. What will the equivalent inductance be? Homework Equations ... The Attempt at a...
  36. Q

    Transient Circuit Analysis: Finding v0(t) for t>0 - Simple Inductance Problem

    Homework Statement In the following transient circuit, assume at t<0, the circuit is at steady state. Find v0(t) for t>0 http://sphotos-b.xx.fbcdn.net/hphotos-prn1/c0.0.277.277/p403x403/550205_509330739086446_705354858_n.jpg Homework Equations The Attempt at a Solution short out the...
  37. J

    Mutual Inductance of Two RC Circuits?

    Homework Statement In the circuit shown in the following figure(Figure 1) the capacitor has capacitance 20 microF and is initially uncharged. The resistor R_0 has resistance 12 Ohms . An emf of 90.0V is added in series with the capacitor and the resistor. The emf is placed between the...
  38. J

    Engineering Finding the inductance of an circuit knowing the energy stored

    If the total energy stored in the circuit below is 190 mJ, what is the value of L? IS = 2 A R1 = 250 Ω : R2 = 38 Ω C = 41 µF Give your answer to the nearest whole number, in mH (I have attached the diagram) I first try to find the equivalent impedence knowing that the impedence of an...
  39. P

    Energy Stored in an Inductor, calculating inductance

    Homework Statement The electric-power industry is interested in finding a way to store electric energy during times of low demand for use during peak-demand times. One way of achieving this goal is to use large inductors. What inductance L would be needed to store energy 3.0 (kilowatt-hours)...
  40. J

    Mutual Inductance dot convention?

    Could anyone give me a link that explains or simply explain to me how the dot convention on the mutual inductance works? For example, I'm trying to draw an equivalent circuit that converts the dots into voltage sources of this circuit...
  41. A

    Create Inductance Vs. Current Analysis/Graph in SPICE (Multisim)

    Is there a way to create an Inductance vs. Current analysis/graph in SPICE (NI Multisim)? In Multisim there is a "User Defined Analysis..." under Simulate -> Analyses and I was wondering if someone knows how to configure this or did some sort of application related to this. Thank You.
  42. A

    Create Variable Inductance in SPICE

    I'm trying to create a variable inductance in SPICE, specifically in NI Multisim. What I'm trying to do is create a saturable inductor. I need an inductor that changes it's inductance with current. Multisim does have a "virtual" inductor that you can create a inductance function with but I can't...
  43. K

    Orientation of magnet relative to coil and it's effect on inductance

    Say I have a coil that is stationary and I have magnets that move past it in a fashion similar to the example in this video: . What is the optimum orientation of the magnet and coil to induce the most current? I know I will want to optimize the rate of change of magnetic flux through the coil as...
  44. J

    Inductance not working in simple circuit

    I want to create a simple circuit consisting of a power source and an inductor. I have a simple circuit consisting of a battery and a wire wound into a solenoid, then separated by a thin layer of air is another solenoid that is connected to a multimeter. Both solenoids have a similar diameter...
  45. K

    Inductance in a magnetic circuit

    Homework Statement I have a magnetic circuit with a coil wrapped around the centre "leg" of the core as follows. I have been given average lengths, areas and permeabilities for the three legs and the airgap. Homework Equations L = (N^2*µ*A)/l The Attempt at a Solution For the...
  46. N

    Inductance of inductor in large steady state magnetic field

    So would the inductance of a inductor be effected if it was in a large steady state magnetic field. Say the inductor produces a field of about .01 Tesla and the large electromagnet produces a field of 1 Tesla or more. How would a high permeable core vs a air core effect it? Would it add...
  47. E

    Electromagnet Design - Value of inductance L

    Homework Statement Hi all, I am working on an electromagnet design. It is a C-shape with an air gap of 80mm. The number of coil windings is 320 turns. I would like to generate let's say B = 30 mT = 300 gauss in the air gap. Area of air gap Ag = 80mmX80mm = 6.4e-3. Mean length lg of...
  48. H

    Why is the misconception of zero inductance for a straight wire so widespread?

    It is zero, contrary to published formulas. I assume that we are talking about a single wire, not about a twisted bunch of wires. Why is the misconception so popular?
  49. S

    How Does Inductance Affect a DC Circuit?

    An inductor of negligible resistance and an inductance of 0.2 H is connected in series with a 330 Ω resistor to a 12V d.c. supply. Determine: (a) the time constant of the circuit (b) the voltage drop across the inductor after two time constants (c) the voltage drop across the resistor after...
  50. J

    Inductance between a polyurethane surface

    I am interested in creating an electric circuit that travels through a polyurethane surface. My plan is to set up two electrodes separated by the dielectric material. My question to the wisdom of the internet is how much current will be lost through the polyurethane surface. I am looking for...
Back
Top