What is Inductors: Definition and 132 Discussions

An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a coil.
When the current flowing through the coil changes, the time-varying magnetic field induces an electromotive force (e.m.f.) (voltage) in the conductor, described by Faraday's law of induction. According to Lenz's law, the induced voltage has a polarity (direction) which opposes the change in current that created it. As a result, inductors oppose any changes in current through them.
An inductor is characterized by its inductance, which is the ratio of the voltage to the rate of change of current. In the International System of Units (SI), the unit of inductance is the henry (H) named for 19th century American scientist Joseph Henry. In the measurement of magnetic circuits, it is equivalent to weber/ampere. Inductors have values that typically range from 1 µH (10−6 H) to 20 H. Many inductors have a magnetic core made of iron or ferrite inside the coil, which serves to increase the magnetic field and thus the inductance. Along with capacitors and resistors, inductors are one of the three passive linear circuit elements that make up electronic circuits. Inductors are widely used in alternating current (AC) electronic equipment, particularly in radio equipment. They are used to block AC while allowing DC to pass; inductors designed for this purpose are called chokes. They are also used in electronic filters to separate signals of different frequencies, and in combination with capacitors to make tuned circuits, used to tune radio and TV receivers.

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  1. Dario56

    I Which law defines the AC inducing voltage in the inductor?

    If we connect an inductor without ohmic resistance to the alternating voltage source, voltage should induce in the inductor because of the Faraday's law. Voltage is induced by changing magnetic flux through the inductor which is accomplished by alternating current through it. Therefore, in order...
  2. yucheng

    Symmetrical parallel inductors, different currents? State Preparation

    We have there parallel inductors (i.e. having the same voltage) with the same inductance, having different currents at a particular time. It appears that this is only possible if the current phasors have different phases See bottom left of video below, ##I_1, I_2, I_3## (time already set to...
  3. malawi_glenn

    Where to Find mH Inductors for Banana Plugs in Basic Electronics Labs?

    Hi all physics teachers I am looking for inductors in the range mH for usage with banana plugs for basic electronics physics labs (like resonance in RLC-circuits etc). I know I can build my own very simple, but if you know a place where I can buy those pre-made I would be very helpful :)
  4. S

    B Phase Difference of Current & Voltage: Capacitors, Inductors & Complex Numbers

    how does capacitors and inductors cause phase difference between current and voltage? how does complex number come into play to explain the relation between phase of current and voltage?
  5. johnsmith7565

    Engineering Series-Parallel Combinations of Inductors

    I am not sure where I made the mistake. If someone could point that out that would be much appreciated!
  6. Franklie001

    AC circuit analysis involving resistors and inductors

    Summary:: Hi anyone can explain me how to solve this circuit, finding the current I2 and I1? Really don't know where to start Thanks
  7. U

    Electrical circuit problem (resistors, capacitors, inductors )

    I did try redrawing the circuit at steady state , but I'm not really sure. I have attached the circuit that I tried drawing, I assumed the branch with the capacitors to be absent at steady state since current won't flow through them anyway. With this diagram I get the correct answer for Q 19 ...
  8. boysenbeary

    Engineering Finding Time Constant T Without L for an LR Circuit

    Edit: Picture of the Circuit (Simple RL circuit) The value of L is not given. Attempt to Solve for T by Rearranging Equation 1: I rearranged the equation to solve for T, using Ohm's Law so solve for I = V/R at each time. https://www.desmos.com/calculator/qlb2n6w4bg This graph is...
  9. Bilbo B

    Inductors in alternating circuits

    Placing an inductor in the first place in an ac circuit will start opposing the current but after a long time it behaves as it were never there and current flows constantly, problem is what happens to energy while opposing? Does it gets stored in the inductor? After when you open the circuit...
  10. J

    How does the current divide in parallel inductors?

    I apologize using English fluently because I am not an Enlgish speaker. When I tried to solve this problem, I used current divider rule. So, $$i_o(t) = \frac{3}{3+5}*4e^{-2t} = 1.5*e^{-2t} A$$ However, This was wrong. The answer is $$ 1.5*e^{-2t} + 0.5 A$$ If I use $$V_O = L*\frac{di}{dt}$$...
  11. R

    Is Energy Conservation Preserved in a Circuit with Two Inductors?

    The standard assumption is that the current through an inductor must be continuous such that you don't produce an infinite back emf. However in this case, the current through ## L_1## is finite before opening the switch and the current through ## L_2 ## is zero before opening the switch. When...
  12. S

    Conservation of energy when placing two inductors next to each other

    This is more like a theoretical question of my own than actual homework. Say there is a circuit with a current source and an inductor. There is a current ##i(t)=at## going through the inductor. We now place a new circuit with an inductor and a resistor next to it. The current ##i(t)## causes a...
  13. D

    Calculating Spatial Current in Resonant Inductors

    Hello, I would like to replicate the results from the paper "wireless power transfer via strongly coupled magnetic resonances", but I'm having trouble interpreting their equations. I'm creating a MATLAB script to do so. In the paper, they get to a point where L and C are to be calculated in a...
  14. C

    I How do I calculate the expected Gain?

    I am doing an experiment in electronics with AC RLC circuits, But there are a few things about what I need to do that I don't understand. First: While I know in the circuit diagram we include the internal resistance of the Inductor in series, but I don't know why we include it in series rather...
  15. Zack K

    How exactly do inductors work in an LC circuit?

    I understand Faraday's law and about induced electric fields created by a changing magnetic fields, etc. But what causes the current to oscillate in an LC circuit, with no battery? If you picture that there is current going into an inductor, and that current is decreasing over time, then you...
  16. iVenky

    Pattern Shielding for inductors in Integrated Circuits

    I have a bunch of questions on pattern shield for inductors in Integrated Circuits (ICs). Basically, shields are made using thick metals (less resistance) to reduce the coupling to the substrate (which are more lossy generally) in order to improve the Q factor. They are patterned to avoid eddy...
  17. G

    Dot convention inductors in series: equation confusion

    Homework Statement So I'm really confused with mutual inductors and dot convention. If your answer is going to be a link to any website I can assure you I read them all and that only left me more confused. So here are my questions: Homework Equations 3. The Attempt at a Solution [/B] ->...
  18. G

    Two voltmeters in parallel measure these different voltages

    Homework Statement I'm currently studying induction law and circuits with inductors. I came however with the following circuit: [1]: https://i.stack.imgur.com/ghaiE.png Homework Equations 3. The Attempt at a Solution [/B] Now my text says the following: "Unlike what your intuition might...
  19. A

    Equations for three inductors connected together

    I have a system with three inductors connected together at a common point. The unconnected ends of each inductor is connected to an independent voltage source. Basically I want to get three expressions for the dynamics of the currents with V1, V2 and V3 as inputs. i.e. i need to eliminate the...
  20. R

    What happens to the energy in an inductor or capacitor when opened?

    Hi guys..i have got a question...suppose i connect an inductor to a dc source until it is fully charged..as soon as it gets full of magnetic energy,i disconnect it from the circuit..remember that it has magnetic potential energy..suppose an idiot like me opens up the inductor (as inductor is...
  21. P

    Behavior of inductors -- Why flux linkage does not change instantaneously?

    Why is it that the flux linkage does not change instantaneously ? is it some property of magnetic fields?
  22. D

    Dealing with two circuits connected by adjacent inductors

    Homework Statement Here is the problem: Homework Equations Typical RL circuit equations. The Attempt at a Solution My main question with this problem is figuring out what to do with the third resistor, the one on the right. Initially, I thought of using RL circuit equations with the left...
  23. 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...
  24. R

    Inductors Technologies: Molded vs. Air-Turned

    Hello. Just a basic question : is there any difference ( Q, parasitic capcitance ... ) between molded inductors and air inductors turned by hand. Let say for instance for values in order of 1 µH ?
  25. Chris Fuccillo

    Looking for LT for three or more parallel aiding inductors

    I need to calculate the mutual inductance between multiple aiding coils. The above formula is fine for 2 inductor but I'm looking to calculate the mutual inductance for up to 30 or more parallel coils wound on the same magnetic core. I can not find an example or formula for more than two coils...
  26. Cocoleia

    Current and voltage with inductors and capacitors

    Homework Statement I am given the following circuit: and asked to solve for v(t) and i(t) Homework EquationsThe Attempt at a Solution If this is right, I don't know where to go from here.
  27. Cocoleia

    Finding current in circuits with inductors and capacitors

    Homework Statement I am practicing these types of problems, for example: and I am asked to find i(t) in this case, and it is in steady state. I really need someone to walk me through these types of problems, how do I get them started. Homework EquationsThe Attempt at a Solution I am really...
  28. 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?
  29. S

    How Does an Inductor Affect Current Change Upon Switch Closure?

    Homework Statement In the following figure, R1= 3.1 Ω, R2= 4.9 Ω, L1= 0.155 H, L2= 0.2 H and the ideal battery has ε = 5.6 V. Just after switch S is closed, at what rate is the current in inductor 1 changing? Homework Equations { \varepsilon }_{ induced }\quad =\quad L\frac { di }{ dt } \\...
  30. L

    Type of resistance imposed by eddy currents in inductors?

    I've got a rather simple inquiry, but I haven't been able to get a straight answer via Google searches. When evaluating the impedance of an inductor, do eddy currents represent a series resistance through, or a parallel resistance around the ideal inductor? I've read that eddy currents are...
  31. P

    How do inductors store energy as a magnetic field?

    My last lecture that I have had, was in inductors. My professor said that they resist changes in current, because they store energy inside the inductor as a magnetic field. I know that as soon as you shut off the energy between the inductor, it starts to dissipate, slowly, until it is completely...
  32. I

    Energy of Inductors in AC Circuit

    Hello, In my textbook, it says that if we have a pure inductor connected to an AC source, the average power is zero. It explains that this is because the energy is used to create a magnetic field for the inductor and then it is extracted to the AC source. So how is it possible for the...
  33. P

    Impedance of capacitor and inductors

    I do not understand how to solve capacitors and inductors with impedance. I do not even know what it is that they use it to solve for. My understanding is that the define the source as a sinusoid using the complex exponential form, and that all voltages and amperage are now also complex...
  34. S

    Current flow across inductors in Series

    I can't articulately ask the question so I drew a diagram. In the diagram, both capacitors are equal in capacitance. The bottom inductors are both 10000 nh and the top are 100 nh. A. Will the capacitors charge at the same time? B If we switch the large inductors to the top and the small to the...
  35. S

    How do Capacitors and Inductors Add/Remove VARS in AC?

    To my understanding, capacitors cause the current to lead the voltage which adds VARS to the circuit and inductors cause the current to lag behind the voltage which removes VARS (in AC circuits). Also, it is my understanding that VARS increase voltage. I work for one of the largest utilities...
  36. Suraj M

    What is the Current Passing Through a 5mH Inductor in Steady State?

    Homework Statement Find the current passing through the 5mH inductor in steady state. Homework Equations I=V/R The Attempt at a Solution Since it says steady current, so no change in current which implies that the inductors act as conductors so the current should just split equally So I...
  37. kostoglotov

    Does Increasing Current Add Resistance in an Inductor?

    I understand why slowing the current, causing a decrease in the flux, momentarily increases the current (stabilizing). I can use the right hand rule and Lenz's law to picture what is happening in that case. But why does increasing the current add resistance? The induced magnetic field is...
  38. A

    How does looping a wire make it an inductor?

    Background: When electricity travels through a wire it creates a magnetic field around the wire. Creating the magnetic field requires energy, which is stored in the magnetic field. So, if we have a length L of wire and wrap it in a small loop of say 100 turns, it becomes an air core inductor...
  39. Passionate Eng

    Understanding Capacitor and Inductor Behavior: A Physically-Based Explanation

    Physically, can someone explain why does not the voltage on the capacitor change immediatly? and why does not the current in the inductor also do? :smile:
  40. C

    Need help understanding inductors

    I'm having a hard time visualizing what is happening in an inductor and why it is happening. I understand the graphs and practical application but I can't seem to physically understand what is happening as you pass current through the inductor besides the fact that it builds a magnetic field...
  41. bradzyc

    How inductors are affected by other factors

    Hi all, A few basic questions regarding inductors really. I'm just doing a bit of reading into these little beauties and trying to get to grips with the workings. My questions are: 1.) Do inductors generate larger magnetic fields with DC or AC? (Providing the same current and voltage) 2.) If...
  42. N

    Optimizing Inductor Design: Factors to Consider

    If I am making my own inductor following the equation:
  43. B. Vane

    RCL Circuit: 2 Resistors, 1 Capacitor, 2 Inductors

    Homework Statement NOTE: Image uploaded with thread shows problem in clearest possible form. V = (45v)sin(80[pi] t) Resistors 1 and 2 = 50 Ohms Inductor 1 = 20 mH Inductor 2 = 2.5 mH Capacitor = 50 uF a) Find the power dissipated by each resistor. b) At what frequency will both resistors...
  44. C

    Joule thief : number of turns around the ferrite core

    Hi everyone, I have to build a simple Joule thief circuit for school. Here it is :(http://upload.wikimedia.org/wikipedia/commons/8/83/Joule_thief.png). The resistance of the resistor is fixed to 1 kOhms, the voltage across the "dead battery" is about 1.5V, the transistor needs about 0.7V to...
  45. A

    Inductive Circuit and Frequency

    Homework Statement A resistor and a capacitor are connected in series to a variable frequency supply. A voltmerter is connected across the inductor and another across the resistor. The supply voltage is kept constant as frequency of supply is increased. State and explain the changes in the...
  46. A

    Inductor Role in Time Constant of a DC Circuit

    A d.c circuit consists of a switch, lamp and inductor. The inductor is replaced with an inductor with twice the number of turns in the coil of wire, nothing else about it is changed. State the effect on A) maximum current B) the time to reach max current I thought increasing the turns would...
  47. P

    Are inductors so powerful?

    hello! are inductors so powerful that the magnetic field generated in their coils to be strong enough to resist the electron movement inside their wire? I find that hard to accept any hint? thanks!
  48. P

    Why capacitors and inductors affect the phase and resistors

    hello! why capacitors and inductors affect the phase of both current and voltage of a AC circuit and resistors don't? let's say we have an AC circuit with resistors only, then there is no change in the voltage and current as imposed from the voltage/current source, right? but what happens...
  49. T

    Can Three Inductors in a Circuit Act Like a Capacitor?

    Hyperthetically, say you had three inductors that each were ideal (90 deg lagging each) pf of zero. So there is a circuit with some current limited supply and you series these inductors up and excite the circuit. Is it going to look like a capacitor because the total angle is 270o like a...
  50. ranju

    Time constant of inductors in machines

    We know that all machines or devices working on AC have high value of time constant so that there is n damage to inductor while current reversal & high value of time constant means increase in time to reach steady state as we can see in fans , coolers , etc. but the tube-lights also have a...