Inductance Definition and 495 Threads

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.

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  1. Ron Burgundypants

    Altered inductance around a solenoid in a cryostat (from Eddy currents?)

    I'm trying to use a solenoid to measure the magnetocaloric effect of dysprosium. The effect is highest at the Neel temp which is down near 180K. I have a solenoid in a cryostat to get the correct temperature. The cryostat's heat exchanger is made of a thick copper cylinder and I think it is...
  2. I

    Mutual Inductance of Coaxial Tube and Coil

    In my lab we are working with a Coaxial coil and stainless steel tube, and are aiming to find the mutual Inductance. I've done some looking around and have easily found the Inductance of a Coaxial cable, and for that of Coaxial coils, but am having trouble with a combination of the two. The...
  3. billyray

    Mutual Inductance Homework Help: Q4d Stuck, Need Advice

    Homework Statement I have included the questions and circuits. I have used previous post to help but am still stuck Homework Equations included in files The Attempt at a Solution I have worked hard to get to the question 4d. I am stuk because using previous posts to help I do not know if I...
  4. A

    Mutual inductance and magnetic feild

    hi, in this problem here there's 2 perpendicular coils but in solution there's an effect of mutual inductance why?
  5. A

    Mutual inductance of a coil inside a solenoid

    Good day , i have an issue with the derivation of the mutual inductance of coil inside solenoid formula I1 is an alternating current which means that B is varying, and we know that the Flux 21 is equal to the integral of the dot product of B and A2 but as B is varying we CAN NOT take it out...
  6. J

    Inductance: Can L1 and L2 be replaced by an equivalent inductor in Figure 4(b)?

    Homework Statement (c) See if you can show that L1 and L2 can be replaced by the equivalent inductor, Leq, of FIGURE 4(b) where Leq = L1L2-M^2/L1+L2-2MHomework EquationsThe Attempt at a Solution [/B] I+I1+I2 Leq = V(L2-M)/jω(L1*L2-M^2) + V(L1-M)/jω(L1*L2-M^2) =...
  7. J

    Inductance of a double circuit line -- struggling with return the path

    So for inductance of transmission line book says formula H = 2 * 10 -7 Loge { [Ds]/[Dm] } I'm struggling to understand self and mutual geometric mean distance. Here is one solved example and for this they've drawn And they say that let a a' form one connection and let b b' form other...
  8. mayank pathak

    Is the Work Done in Charging an Inductor Different in Non-Quasistatic Scenarios?

    As we know, work done by an outside agency in creating some current ''I" in an inductor 'L' is 1/2LI2. Now this result is derived by quasistatic approximation if I am not wrong. Now, I am assuming that in non quasistatic (real) scenarios, the work done by outside agency would be different(If you...
  9. Z

    The origin of self inductance in a current loop?

    Hi Forum I am trying to get a better grasp of the relation between electric field and the magnetic field. The overall question is "What is The origin of selfinductance in a current loop?" Here are my thourghts: A battery is connected to a say circular wire with some resistance. The current...
  10. E

    How to calculate the inductance of a stator winding

    Hi there, i have a three phase synchronous generator that is powered by a 1/3hp electric motor. I am having difficulty calculating the inductance of each phase of the stator winding when it is at full operation. I will give you some of the specs of the alternator. The rotor has 12 poles, with an...
  11. T

    B Plural of henry?.... henrys? henries?

    What do you reckon, is it henrys or henries?
  12. T

    Magnetic flux and inductance?

    If a current flows in a straight wire, a certain amount of magnetic flux will be generated around it. Now suppose I put an iron tube around the wire (but don't change the current). I know the inductance will increase, but is that because more total flux is now being generated, or is the total...
  13. B

    Why does VFD cable data sheet show Inductance, Capacitance?

    Can someone point me to an understanding of why VFD rated cable include Inductance and Capacitance? For example, Belden cable 29504 shows impedance, inductance, capacitance between conductors, capacitance between conductor and sheild, and DC resistance. Is there a VFD motor calculation that is...
  14. M

    Question on corner and resonant frequencies

    Homework Statement 1. An RC filter is constructed by modifying a voltage divider. The top resistor R1 = 3kOhms remains the same but the bottom resistor R2 is replaced by a capacitor C = 8nFarads. Determine the corner frequency fc for this filter in kHertz. 2. For an RLC circuit R = 12.4...
  15. M

    Question about Capacitance and Inductance

    Homework Statement [/B] Hey everyone, I recently got two problems on capacitance and inductance and need some help on them. Here are the two problems: 1. A Royal Red Robin Burger contains 1230 food calories. Also, more that the daily requirement for protein, fat, sodium ..., even without fries...
  16. E

    Effect of saturation on transformer inductance

    Hi all How is the inductance affected when the transformer core has reached saturation? I can not seem to get my head around it, and I hope someone can help me understand it, thanks. Kind wishes
  17. ESMAT 1995

    Constant current source Inverter

    i was reading about CSI and the first paragaph said "A constant current source is assumed here, which may be realized by using an inductance of suitable value, which must be high, in series with the current limited dc voltage source. " and it says nothing else about it , so clearly it's a basic...
  18. F

    Inductance in FEMM 4.2, series/parallel connection of coils

    Dear Forumers, I have an axisymetric magnetics problem in FEMM 4.2. I'm analyzing a loudspeaker motor (permanent magnet included) with many coils. I would like to get the inductance for the coils connected in series and in parallel. Let's say that I have 2 coils, coil A (n=N1) and B (n=N2)...
  19. B

    What is the relation between inductance and reluctance?

    Hi, say for example we have a magnetic core with a coil wound around, and if we introduce an airgap (i.e. increasing the reluctance), how is inductance reduced? I read on some forum (see source below) that inductance scale inversely with reluctance. So I do not have the mental picture of why...
  20. B

    Does a solenoid get warm with inductance?

    Hi, I'm wondering if a solenoid is only hot by copper resistance or in addition with the inductance produced into the coil too ? Another small question : in the sofware Femm there is a computing result parameter called "voltage drop"; does it means you need ( at least ) x volt to get the...
  21. peroAlex

    Electromagnet with two cardboard pieces

    Hello! Recently I was going through some old exams and upon encountering this problem (which seemed pretty easy) I got stuck. Exams at my university are composed of individual tasks, each having three subquestions with four plausible answers respectively. Solution sheet gives results only, so...
  22. J

    Inductance and Capacitance as the Secondary Load

    What are the effects of adding inductance and capacitance as secondary load of transformer? I am using a Ring /Toroid Transformer.
  23. R

    Mutual Inductance of two coaxial coils

    Homework Statement Two coils of the same length and almost the same cross-section are put one inside the other. Find their mutual inductance if the self-inductances are and . Homework Equations 1) \phi_i=L_i I_i 2) \phi=\iint_A \vec{B} \cdot d\vec{A} 3) \phi_1=M_{12} I_2 The Attempt at...
  24. T

    One coil twisted in a figure 8 vs. two coils side-by-side

    The side by side coils are round or oval, and wired together in series. Let's say the side by side coils are wound opposite (one clockwise and one counterclockwise) to match the direction of travel of the twisted coil's loops. Each of the side by side coils has the same number of turns as the...
  25. peroAlex

    Flux and Current of Magnetic Core With Air Gap

    I am a student of electrical engineering. This task appears in our textbook. However, there were no solutions provided. I tried understanding the task but got lost in the process. This is why I seek help here on this site. I would like to ask you for guidance and any sort of advice on how to...
  26. B

    Measuring a DC motor's inductance

    Hello, on the internet, there are various methods on measuring the inductance. For example, http://www.dos4ever.com/inductor/inductor.html and https://electronics.stackexchange.com/questions/182116/whats-the-easy-way-to-measure-a-dc-hobby-motors-inductance If I want to measure the inductance...
  27. A

    What happens to a coil of wire as current is increased?

    Homework Statement Homework Equations L = (N * F_b) / I (where F_b is the magnetic flux) emf = -L * (dI/dt) The Attempt at a Solution I originally thought that the inductance would decrease since it is inversely proportional to current. But, looking at the equation for emf, that would...
  28. A

    Simple inductance question: Finding steady state current

    Homework Statement Homework Equations I = E / R_total The Attempt at a Solution I mostly just want to clarify that my thinking is correct. The solution for this problem shows that the current is split evenly between the two paths. Is that because we're assuming that the inductor has no...
  29. jlmccart03

    Find current through inductor after many time constants.

    Homework Statement In the figure, R = 1.9 kΩ and ε0 = 60 V . When the switch is closed, the current through the inductor rises to 10 mA in 30 μs . What will the current in the circuit be after many time constants? Homework Equations I = V/R or I = ε/R if current is constant which after many...
  30. cheapstrike

    Self inductance of a coaxial system of cylinders

    Homework Statement A thin hollow cylinder of radius a is surrounded co-axially by another hollow cylinder of radius b, where b>a. An electric current I flows through them (I is into the plane of paper (x) in outer cylinder and coming out of plane of paper (.) in inner cylinder). Find the: a)...
  31. G

    Comparing inductance and capacitance: Analogy to charge

    Hi. Inductance and capacitance have many analogies, both conceptually and formally. A capacitor connected to a voltage source carries the charge ##Q=C\cdot V##. The analogous equation for inductance is ##n\cdot \Phi=L\cdot I##. Charge is physical, it's proportional to the number of excess...
  32. G

    Why do some devices work for a short time after unplugged?

    Hi. Some laptop or mobile phone chargers still work for a couple of seconds after being unplugged. I've also seen similar behaviour with the standby lights of monitors, TVs and other devices after they are disconnected from power. Is this due to self-inductance in the transformer? If so: If...
  33. A

    Mutual Inductance: Rectangle w/ Variable Height

    Homework Statement I have a shape that is basically a rectangle but one side increase in height(shape length is L and it increases height at L/2). Which leaves me with two squares of different heights. Can I find the mutual inductance of each square and then add them up to find the inductance...
  34. Cocoleia

    RL circuits - finding resistance and inductance

    Homework Statement I am practicing questions from the book in preparation for an exam, and I am having trouble with this one Homework EquationsThe Attempt at a Solution According to my professor, the answers are: R1=12ohm, R2=9ohm, L=34.28 H So far this is what I have done: Voc = 6V τ = 20/7...
  35. G

    Self inductance of a superconductor

    Hi. Superconductors can be made hover above or even below magnets. As far as I know, this can be interpreted as an extreme form of Lenz's law: Eddy currents on the surface of the superconductor create an opposing force that is able to cancel gravity since the currents aren't affected by...
  36. F

    Trying to model mutual inductance with losses

    So as a learning project I am trying to solve a transformer with losses but I am stuck. 1 coil L1 with N1 turns is excited by a sinusoidal voltage V1 with a resistor R1 in series. Wound around a common core with a second coil L2 with N2 turns and a resistor R2 also in series...
  37. A

    Inductance per unit length of coaxial transmission line

    1. Homework Statement An air coaxial transmission line has a solid inner conductor of radius a and a very thin outer conductor of inner radius b. Determine the inductance per unit length of the line. Homework Equations the book states the methodology to find the inductance as follows: 1)...
  38. Conductivity

    How does Faraday's law include self inductance?

    A varying magnetic flux causes an induced voltage (according to Faraday-Lenz law) that generates a current that generates a magnetic field that generates another magnetic flux in the same circuit. Does the Faraday-Lenz law include this self induction? In other words why can't we take that...
  39. L

    Why are there two terms of both mutal and self inductance

    Homework Statement Given two inductors, connected in parallel connected to a battery, why do the following emf relations hold? $$\mathcal{E}_1 = - N_2 A \frac{d B}{d t} = -M\frac{d I_1}{d t } \\ \mathcal{E}_2 = -L_2 \frac{dI_2}{dt}- M \frac{dI_1}{dt}$$ See attachment ! Homework Equations...
  40. H

    How Do You Calculate Mutual Inductance in Toroidal Solenoids?

    Homework Statement A toroidal solenoid with mean radius r and cross-sectional area A is wound uniformly with N1 turns. A second toroidal solenoid with N2 turns is wound uniformly on top of the first, so that the two solenoids have the same cross-sectional area and mean radius. What is the...
  41. A

    How to calculate the mutual inductance?

    Homework Statement A long solenoid has a radius of 3 cm, 3000 turn per meter, and carries a current I = IOcos(ωt), where Io is 0.25 A and ω is 628 s−1 . It is placed through a circular loop of wire, radius 5 cm, which has resistance 100 Ω. The magnetic field in a solenoid is B = µonI. (a) Find...
  42. N

    Mutual inductance / equivalent inductor

    Homework Statement Homework Equations See if you can show that L##_1## and L##_2## as in (a) can be replaced by the equivalent inductor L##_{eq}## as in (b): $$L_{eq} = \frac {L_1 L_2 - M^2 } {L_1 + L_2 - 2M } $$ The Attempt at a Solution Um, I don't really know where to start because I...
  43. K

    Inductive charging: Emf induced in two coil loops

    Homework Statement So I'm trying to figure out this problem: The base of our charging station is composed of a coil with N1 turns and area A1 connected to a 120 VAC, 60 Hz source. The device has a smaller coil with N2 turns and area A2, which when attached will fit completely inside the...
  44. EddieP

    How does the core size affect an Inductor's efficiency?

    Hello, I am wondering if anyone can help me with the following question. I want to find out how the size of the core in an inductor influences the current induced in the secondary coil, and whether a smaller core is more efficient if efficiency is defined as inducing the highest current in the...
  45. J

    In power transmission why inductance L increases with increased spacing

    In power transmission where single phase power is transmitted in 2 wire AC system. Now inductance is The equation for inductance is then: L = 2 X 10-7 In(De1/4/rx) Why does inductance increase with increase in distance between conductors? When the spacing is increased, the air gap increases...
  46. Kfir Dolev

    Combine capacitors and inductors to be frequency independent

    Is it possible to combine (possibly infinite) capacitors and inductors to get a total impedance which is independent of frequency. If so, how?
  47. O

    Why does a voltmeter measure a voltage across inductor?

    The potential difference across an inductor is supposed to be zero, but a voltmeter measures it to be L*dI/dt. Also, if the p.d is zero then the electric field in the wires of the coil will be zero and in that case, why should charges flow at all? What am I missing?
  48. J

    Finding Inductance: Solving Homework Statement

    Homework Statement See attached image. Homework Equations The only equation that I have learned to find inductance is : L= μ N2 A / ι However, when I do this, I get the incorrect answer. I am not so sure what is going on in the given solution and was wondering if somebody could explain that...
  49. B

    Power Factor Correction: Metering & Inductance

    I am sure this has been discussed many times before but here goes. I was recently working on motors with a power factor cosine of 0.69. To counteract this the company installed banks of capacitors to get the power factor near 1. My question is this, the capacitors were installed downstream from...
  50. B

    Calculate the inductance of thick solenoid by ansys maxwell

    hello, how we calculate the inductance of thick solenoid by ansys maxwell ..!:wideeyed:
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