What is Inductor: Definition and 454 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. 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...
  2. I

    Can't tell if I made a chaotic circuit or if I broke the sim

    So, I was playing around with a couple of voltage multiplier circuits a few months ago, and while optimizing one design, I came up with a pretty neat (not to brag) way of converting a sine wave to a square wave by using transformers in a completely different way than normally. A little while...
  3. C

    Variable resistor & inductor connected to alternator

    A simple 2 pole alternator (a synchronous generator), is powered by a steam turbine. The amount of steam to the turbine is kept constant with a constant pressure ##p##, flow rate ##\dot{q}##, and power ##P##. If a variable resistor, inductor, and capacitor are connected in series to the...
  4. S

    Finding the current Io for t>0 in a RL circuit

    Homework Statement For the circuit in the attached file, find io (current) for t>0 Homework Equations The Attempt at a Solution I have included an attachment which shows the solution. However, I will copy the solution here as well for reference: When t<0, the switch is closed, the inductor...
  5. jcoona

    Engineering RLC Series Circuit: Understanding Inductor Behavior

    Homework Statement I am not sure how an Inductor behaves in an RLC Series Circuit Homework Equations The Attempt at a Solution I know that after a long time, that the circuit above, the voltage in the capacitor is max. Generally, I also know that the current through an inductor after a...
  6. T

    Magnetising current of inductor and transformer, onformation

    Hi, I've never thought of an inductor actually consuming any real power, however the other day I was concidering an open circuit secondary, transformer. This should be the same model as just an inductor should it not? (or rather this is how we can model an inductor too?) If this is so all the...
  7. S

    Capacitor with magnetic dielectric

    Odd question, would anybody know what would happen if a parallel plate capacitor (good conductor) had a soft magnetic material (fairly poor conductor) as a dielectric? What would be the DC/AC electrical characteristics of this?
  8. S

    Finding the equivalent resistance of an RL cct & step input

    Homework Statement Determine the inductor current i(t) for both t<0 and t>0 for the circuit shown in the attached document"Circuit 1. Homework EquationsThe Attempt at a Solution Before t=0, i=(25)/(3+2) = 5A After t=0, i(t)=i(0)e^(-t/tow) tow=L/R=4/(6/5) However, the...
  9. N

    Why does my inductor coil have no effect on my circuit

    I have the circuit with a drawing below, to create sonoluminescence. One of the steps needed was an inductor coil in order to achieve electrical resonance within the circuit. The link provided here: http://www.macgeisler.de/nld/sbsl-howto.html told me to find the inductance needed through the...
  10. EddieP

    Calculating magnetic field for a micro solenoid

    I am trying to calculate the magnetic field (in tesla/gauss) of an iron core electromagnet that is very small and has very few windings. For example 12 windings over 0.003 meters. I know this is not going to produce a very strong field, but I would like to pulse a strong current through the coil...
  11. S

    Phase Difference between Voltage and Current

    Homework Statement The circuit above has a 29 resistor and a 11.1 mH inductor. Calculate the theoretical phase difference between the current CPA and voltage VPB if the circuit is driven by a sinusoidal voltage source with a peak amplitude of 3.5 V at the following frequencies: 20 Hz 420 Hz...
  12. S

    Engineering Finding the component values of a RLC circuit

    What methods could I utilise to find the individual values of the components - resistor, inductor and capacitor - of a series RLC circuit using an oscilloscope, signal generator and 10 ohm resistor. Where each component can be isolated in order to find the voltage etc. I've already found the...
  13. Salvador

    DC inductor changing reluctance -- effects?

    Hi, I would like to know what happens to the flow of DC current and voltage in an inductor if we change the reluctance of the inductor core repeateadly, Just a DC power source attached to an inductor in series with a lightbulb for example , now as the DC pass through the wire wound around the...
  14. J

    Setting up an LRC series circuit with coupled coils

    Homework Statement I have been trying to set up an LRC series circuit where in place of an inductor we have a pair of coupled coils. My aim is to determine the resonant frequency in the circuit when the voltage across the resistor or the current in the circuit is at a maximum. I am using a...
  15. 2

    Transforming DC to AC: The Role of Inductors and Capacitors in RLC Circuits

    I have only just found out about inductors, and am trying to figure out how a circuit with an inductor and a capacitor could change dc current to ac current. With the set up of the circuit, would it suffice just to have the dc supply with a 'gate' that stops/allows through the dc current with a...
  16. K

    Can plasma create current in an inductor?

    Right, I know that plasma has a very high charge because of electrons doing stuff and that the plasma can be contained and controlled using an electromagnet, but can it be put the other way round? Say I have a chamber with plasma in it, generated by whatever, and I put an inductor outside the...
  17. genxium

    Voltage drop across ideal solenoidal inductor

    First by ideal I mean zero resistance. I tried to verify Faraday's law in simple LCR circuit but ran into some conflicting results. Though the description below will be a little verbose, the configuration for this problem is extremely simple: assume that I put a solenoid...
  18. M

    Why Does Rearranging an Inductor Yield Different Magnetic Fields?

    I found two ways to solve this problem, but I get two different solutions, it's confusing because I can't see the flaw in wrong solution. 1. Homework Statement Long cylindrical inductor of diameter D1 and inductance L1 is connected to battery and creates magnetic field B1. Inductor is then...
  19. BeautifulLight

    Dual voice coil speaker: Each coil get an inductor?

    1st order crossover desired low-pass frequency: 100hz At 8 ohms, that'd be about 12mH. But what happens with a DVC speaker? Each coil get a 12mH inductor? I'd like to think so... Speaker is 8+8 ohms and will be parallelled to a set of 8 ohm extended range speakers showing my amplifier 4 ohms...
  20. D

    Physical resonance of inductor

    17:47 - dlbeeson: Is there any benefit of setting capacitance of an LC tank to resonate an inductor at its natural physical resonance frequency, like a tuning fork frequency? Like a brass pipe hanging on a string in a wind chime, the inductor must also have some physical resonating frequency...
  21. 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...
  22. T

    Designing Inductor, need you worry about saturation?

    Hi, I'm just wondering (theoretically), about calculating magnetic opperating point for an inductor. Say permetivitty mu is 'u', N turns, A area, l is length: Inductance L = u.N2.A / l Then do you need to worry about saturation? Or can you just wrap as many turns around it as you want for a...
  23. I

    Inductor Color Code: 68mH Violet Gray Brown Silver

    hi, i just bought an inductor that was labeled 68mH, but the colors are violet gray brown silver. doesn't this make it 680uH (0.68mH)?
  24. M

    Difference between wirewound resistor and inductor

    Hi. I am looking to understand the difference primarily in construction between a wirewound resistor and an inductor. Both are formed using a coil loop but are clearly behaving differently. Does the coil in a wirewound resistor induce a magnetic field?? Thanks, Mark.
  25. J

    Inductor's output power measurement using spectrum analyzer

    Hello! I have a question about measurement of spectrum analyzer. I made some inductor by lithography, evaporator, and lift-off process, and tried to measure using spectrum analyzer. (The probing was GSG type) I swept the frequency from 100MHz to 5Ghz, and output power was monitored by...
  26. E

    RLC Circuit Frequencies Help

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  27. J

    Series R-L Circuit - Charge/Discharge described properly?

    Hi Rather than ask how it works iv'e studied this a bit (via conflicting sources) and hoping that another member could have a quick scan over and pick out any bits where I've got it wrong? I know its a lot to read, but iv'e tried to keep it as short as possible, so if you could help i'd be...
  28. EnchantedEggs

    Difference between inductive reactance and inductance?

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  29. R

    Engineering Energy Dissipation by Inductor (RL circuit)

    Homework Statement Homework Equations The voltage across an inductor is V(T) = L i' Basic current division and voltage division . Step function where u(T) : when t is smaller than 0 : u(t) = 0 t >0 : u(t) = 1 The Attempt at a Solution The voltage source has...
  30. Rugile

    Heat in a resistor (circuit with inductor and capacitor)

    Homework Statement A source of ε = 10V, capacitor of C = 5 μf, inductor of L = 15 mH and r = 10 Ω and a resistor of R = 100 Ω are connected as in the schematic (attached). How much heat will dissipate in the resistor after the switch is opened? Homework Equations dQ = I2Rdt KVL The...
  31. O

    Can a straight wire be a self inductor?

    I hope this is posted in the correct thread. When I was still in my physics class, we learned that a loop of wire with current can act as a self inductor. Just to refresh my memory: A loop of wire carrying current has a magnetic field around it due to current, however if the current changes...
  32. D

    Guitar Strings and Inductor Coils

    I need a little help with a project I'm working on. Here's the gist of it; I am taking two coils, hooking one into the input of an amplifier circuit and the other to the output. Both coils will be over an electric guitar string. The guitar string when vibrated will have a changing induction...
  33. ranju

    Energy dissipation in inductor and capacitor

    I want to know the meaning of energy dissipation...is eergy dissipation and energy consumption are same things?? inductor and capacitor store energy which can be used later... what is then energy dissipated?? is it the heat loss in these elements?? I mean..heat loss is what we say energy...
  34. T

    Inductor Energy Loss Calculation

    I was so happy with the assistance provide here by NascentOxygen! Great contributor! I have another question: Homework Statement A 20V battery is connected to an inductor with 1000μH that has 1000 turns with a cross section area of 1cm^2 is connected for 0.3 Sec during where 20J energy are...
  35. T

    What Happens to Inductance with Changes in Current and Loop Configuration?

    Hello, I'm new to this forum. I hope I am submitting this to the right thread. Just started physics and I am looking to get a little assistance Homework Statement A single loop carries 100mA and has an inductance of 100μH Homework Equations For air cored L = μ0 * (N^2*A/length) L = Nø/i...
  36. H

    What happens when a piece of iron is put into an inductor?

    Homework Statement You have a circuit with current I running through a solenoid. You insert a small piece of iron into the coil; what happens? Homework Equations d(Magnetic Flux)/dt = -EMF The Attempt at a Solution Iron is diamagnetic, so inserting it will decrease the magnetic field...
  37. D

    Equivalent capacitor for an inductor to make PF=1

    For some reason I had to apply a capacitor in parallel to an AC circuit which has reduced the power factor as a result some power generating AC equipments are complaining (overload). Now I need to apply an inductor in parallel to fix that. For that I need a formula which gives me the...
  38. O

    So, what is the inductor from the extension cord?

    We used to buy these cheap outlet strips that came with really long wires, wound up. They said to unwind them before use because they caused fires. I thought it was inductance. But now that I think about it, there's not just a single conductor with AC in there. There's also ground and...
  39. A

    A resistor, an inductor, and a capacitor are connected in series?

    Homework Statement A resistor, inductor, capacitor are connected in series to an AC source. The AC source is operating at the resonance freq. Which are true? 1.The current is in phase with the driving voltage. 2.The peak voltage across the capacitor is greater than the peak...
  40. U

    Inserting iron core in an inductor coil

    Homework Statement A coil is connected in series with a bulb and this combination is connected to a DC source. When an iron core is inserted in the coil, what will happen to the brightness of the bulb? The Attempt at a Solution When the iron core is inserted, the magnetic field...
  41. A

    Induced Emf in an Inductor in an LRC circuit

    Homework Statement In the circuit shown in the figure, the switch S is closed at time t=0 with no initial charge on the capacitor. What is the induced emf if the inductor at time t=0? Homework Equations ε=-LdI/dt The Attempt at a Solution Initially the inductor acts like a broken...
  42. gfd43tg

    Finding inductor value for same current/voltage phase AC analysis

    Homework Statement In the circuit below, what should the value of L be at ω = 10^4 rad/s so that i(t) is in-phase with v(t)?Homework Equations The Attempt at a Solution I am a little uncertain exactly what is meant by i(t) being in phase with v(t). Do I assume that both are cosine functions...
  43. V

    Why doesn't an inductor act as a closed circuit to AC?

    I understand that an inductor acts as a closed circuit to DC because it's just a coiled wire but why doesn't it act the same way for AC? What does it act as in AC?
  44. S

    How to Determine the voltage polarity of inductor in a circuit?

    The Voltage polarity across the inductor is same as that across the capacitor since both are in parallel and the voltage across them must be same. But when Inductor, capacitor and resistor are connected as shown in the second figure what would be the voltage polarity across the inductor and...
  45. neeraj kaira

    Improving 100mW FM Transmitter Design

    What is the use of inductor in a receiver? It amplifies the signal or it only blocks the high frequency signals?
  46. F

    Engineering V1 = 2V Calculate Voltage, Power in Circuit w/ Inductor at t=>0

    Homework Statement For the circuit shown below, the current through the inductor is defined as follows: i(t)=\begin{cases} 0 & \text{if } -\infty <t<0 \\ 1-e^{-2t}& \text{if } 0\leq t < \infty \end{cases} L = 1H, R2 = 2 ohms For t=> 0 find: a) VL(t) b) Vr(t) c)...
  47. Z

    Max Voltage across an inductor

    Homework Statement The current in a 28mH inductor is known to be −10A for t≤0and (−10cos(400t)−5sin(400t))e^(−200t) A for t≥0. Assume the passive sign convention. At what instant of time is the voltage across the inductor maximum? What is the maximum voltage? Homework Equations v(t) =...
  48. N

    Current through inductor as function of time

    Homework Statement The L=100 mH inductor in the following figure has an initial current of Io=10 mA. If the voltage is, v(t)=1e−10t+2e−5t V, what is the current, i(t), through the inductor? Express your answer as a function of time with units of mA. The figure shows an independent voltage...
  49. L

    Potential Difference Across Resistor in Parallel with Inductor

    If we have a resistor and inductor in parallel, how does the resistor maintain a potential difference equal to our emf? Am I correct in saying that for the inductor to maintain a voltage difference, there has to be some change in current, so that the current going through the resistor is also...
  50. C

    Making resonance using simulated inductor (op amp)

    Making resonance using "simulated inductor" (op amp) I want to have a circuit that responds strongly (gives me a good measurable voltage) to a 10kHz sound input. To do this, I thought about hooking up a microphone and making a resonance circuit (using inductor and capacitor) to amplify the...
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