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. G

    Resistor, capacitor, and inductor in series

    Homework Statement A resistor, capacitor, and inductor are connected in series across an AC generator. Which of the following statements is true? The power delivered by the generator does not depend on the phase difference between the generator voltage and current. All the power is lost...
  2. S

    How Does an Inductor's DC Behavior Affect Circuit Current Buildup?

    Homework Statement Assume that resistor R has a resistance of 34.2 Ω, inductor L has an inductance of 152 mH (milli-Henry), and the battery has a voltage of 33.7 V. Also assume that the circuit elements are ideal. If the switch S is closed suddenly, the time for the current to attain a...
  3. G

    Simple Kirchhoff Loop problem with inductor

    Homework Statement Just refer to the figure. The part shown is a part of a big circuit which you and anybody else shouldn't worry about.Homework Equations The Attempt at a Solution I considered the battery terminals to be at 10 and 0V respectively. So the farther end of the resistor should be...
  4. M

    About Direction of current in the inductor in RL circuits

    i'm a bit confused about the direction of current in the inductor in RL circuit, i thought in the charging stage at t(0-) the the voltage drop on it will be in the direction of the initial current, which means the discharging current at t(0+) will be in the opposite direction of the initial...
  5. E

    Measure High Voltage using Coil Inductor

    Hi everybody, I need to indirectly measure the high voltage across a wire, which is one of the leads to a spark gap. I ran the wire through a coil inductor(air core) and measured the voltage across the coil leads with an oscilloscope when i get the spark. I also connected a resistor in series...
  6. P

    Solving a Series Circuit with Resistor, Capacitor and Inductor

    Homework Statement Consider a circuit consisting of a voltage source with V = V_0 \sin{\omega t}, a resistor, a capacitor, and an inductor, all connected in series. The problem is to find the steady state current as a function of omega. Homework Equations V = IZ Z = Z_R + Z_C + Z_L...
  7. L

    How Can I Solve for the Temperature of a Spiral Inductor in Comsol Multiphysics?

    Hi, this is my first post. I'm new in using comsol multiphysics and I'm trying to model a spiral inductor which is placed in an another material (glass) which is over a substrate. The pads of the inductor are outside the material. What I'm trying to find out is, the temperature of the surface...
  8. R

    Capacitor and Inductor in Series

    Hi, if you have a capacitor and inductor in series connected to an Alternating Supply, do their reactances add up? Thanks Richard.
  9. G

    Finding Current Through Inductor via Kirchoff's Method

    Circuit is shown in attachement. At t = 0s, switch S is closed. Find a function for the current through the inductor starting from t = 0s. Using Kirchoff's method, I find that the maximum current through the inductor is .500 A as t approaches infinite and that the total current is 1.50 A...
  10. S

    Pure inductor (only) in AC circuit

    Hello, suppose we have a sinusoidal AC source connected to only a pure inductor of self inductance L ( no resistance at all ) ..then emf induced in the inductor is L * dI/dt and is equal and opposite to the applied emf. but if the induced emf opposes the applied emf , then how can there be a...
  11. S

    Inductor in simple circuit w/ graph Problem Help

    Homework Statement In Figure 30-63, the inductor has 26 turns and the ideal battery has an emf of 16 V. Figure 30-64 gives the magnetic flux through each turn versus the current i through the inductor. If switch S is closed at time t = 0, at what rate di/dt will the current be changing at t =...
  12. M

    Can a capacitor discharge itself through an ideal inductor?

    Can a capacitor discharge itself through an ideal inductor ? If yes state the reason , if No how will the charge on the capacitor will behave ?
  13. J

    Inductor as a differentiator (op amp)

    Homework Statement Sorry this computer doesn't have access to PSPICE and I don't have a scanner, but let's say that I have an op amp. 1) there is a time varying voltage source Vs 2) There is a resistor R1 connected to the inverting input of the op amp 3) The noninverting pin is connected...
  14. M

    DC Battery and Ideal Inductor Circuit Current

    will there be any current in a circuit with an ideal dc battery and an ideal inductor?
  15. R

    Help in working of capacitor & inductor

    please help me in working of capacitor wen we apply sin wave to capacitor in closed circuit& and also resonance physically not mathematically all the above
  16. O

    An AC circuit w/ only an inductor

    i have no idea what it is.. Please help An AC circuit contains only an inductor. Which of the following is correct. a. the current lags the voltage by 90 degrees b. the current lags the voltage by 180 degress. c. the voltage lags the current by 180 degrees d. the current and voltage are in...
  17. K

    Calculating AC Current for a 0.197 H Inductor with 166 V Peak Voltage

    Homework Statement A circuit contains only 0.197 H inductor. An AC voltage of peak value 166 V and frequency 60.5 Hz is applied to the circuit. When the voltage is 166 V, what is AC current? Answer in units of A. Homework Equations The Attempt at a Solution we know that...
  18. S

    Help Solve Inductor Circuit Problem for Test Tomorrow

    Please Help! Inductor Circuit An AM radio antenna has the shape of a coil with inductance 0.90 mH. A radio wave with frequency 1.2 MHZ induces a current of amplitude 5.2 nA in the coil. What is the amplitude of the induced voltage across the coil? I really need your help. It's going to...
  19. I

    Voltage of an Inductor: Solutions to Get 200V

    Hello! I have this circuit: a source connected to an amplifier, which is connected to a coil. I'm trying to get 200V through the coil at 40 MHz. The problem is that the amplifier is not calibrated at that frequency and now I can only extend measurements done at lower voltages, which seems to...
  20. S

    Rate of current changing through an inductor

    Homework Statement At time t=0 a 45V potential difference is applied to the leads of a coil with inductance L=50 mH and resistance R=180 ohm. At what rate is the current through the coil increasing at t=1.2ms? Homework Equations 1) L=EMF/ (di/dt) 2) L=N(flux)/i 3)emf=iR The Attempt...
  21. J

    Loading the magnetic field of an inductor

    Hello all, I have a simple experiment I'm working on where I am pulsing square waves into an air-cored coil with a high inductance (in the mH range). I am wondering if there is a way to calculate what pulse width, on the square wave, I would need to use to completely load the magnetic field...
  22. T

    Can an Inductor Reduce Voltage?

    hi guys... i quiet new here... just wondering ,.. how to measure a inductor... TQ
  23. M

    What is the role of inductor characteristics in smoothing rectified AC current?

    hi I was wondering if anyone would be able to help me out; which inductor characteristic is utilised in the smoothing of rectified ac current
  24. V

    Current across resistor and inductor

    Homework Statement I have a resistor and an inductor in series. The current across each is the same, correct? I want to know if I can use Ohm's Law to solve for current across the inductor if I know the Voltage and inductive reactance. Basically, does I = V/X_{L} ? Homework Equations V...
  25. J

    Calculate Inductance of Inductor: 100v/20A RMS

    Homework Statement a non inductive resistor passes a current of 20A rms, when connected to a 100v rms supply (50HZ). When connect in series with a pure inductor across a 230v supply the combination draws a current of 15A calculate impedance of the circuit, inductance of the inductor...
  26. M

    Understanding Motor and Inductor Emf

    In these two cases , emf will be induced in different way. for motor: current +B-field-->Force-->Coil rotate-->change of magnetic flux-->emf inducedd in the coil for inductor , when the switch suddenly openfrom closes switch, there are a sudden change of magnetic flux ,there emf will be...
  27. S

    Equipment for Hysteresis Loop for Inductor

    What instrument would I need to get a hysteresis loop (Flux Density vs Magnetizing Force) for an inductor? Is it something that can be easily obtained given the proper equipment? Thanks! -Shad
  28. M

    Soft Iron Core Functions in Inductor, Motor & Generator

    I would like to know what is the function of soft iron core? Is there a difference in function when inserting soft iron core in inductor , motor , generator ? Thank you
  29. V

    Phasor circuit problem: 1 resistor, 1 capacitor, 1 inductor, 1 Voltage source

    Homework Statement What value of \omega will cause the forced response v_0 in the circuit below to be zero? http://img248.imageshack.us/img248/1854/problem934ao5.jpg Homework Equations Phasor eqs. The Attempt at a Solution...
  30. D

    Inductor Currents: Find L for 15kHz Oscillator & 6V RMS, 65mA Peak

    Homework Statement An inductor is connected to a 15 kHz oscillator. The peak current is 65 mA when the rms voltage is 6.0 V. What is the value of the inductance L? In mH Homework Equations Il=Vl/Xl Xl=frequency*L The Attempt at a Solution Well I thought this problem was really...
  31. D

    What is the effect of an inductor on current in an AC circuit?

    Homework Statement Imagine a simple AC circuit with a voltage source and an inductor: Determine the current going through the circuit. Homework Equations voltage of the source: v = V_m\sin{\omega}t induced emf in the inductor: e = L\frac{di}{dt} The Attempt at a Solution By...
  32. E

    Recirculation Current in an Inductor

    I am trying to derive an equation for a simple inductive circuit which is the serial connection of an inductor (L), a resistor (R) and a Diode (D). The initial condition is a current flowing (Izero). Using Kirchhoff's law, the basic equation is: Vdiode=Vinductor+Vresistor The inductor is...
  33. P

    Solving a Differential Equation for Parallel Circuit with Capacitor, Resistor, and Inductor

    I have a circuit with a capacitor, resistor, and inductor all in parallel with each other. I have to write the differential equation governing the voltage. However, when I attempt to do that [using Kirchoff's Voltage Rule] I will end up with: Vc + Vl = 0 and Vl + Vr = 0 However, this implies...
  34. Amith2006

    Engineering Inductor in D.C Circuits: Exploring Self-Inductance and Induced E.M.F

    1) A bulb is connected in series with an inductor and a 6 volt D.C supply. A soft iron core is inserted into the coil quickly. It is said that there is a momentary increase in the intensity of the bulb because at that particular instant the induced e.m.f is greater than the e.m.f of the source...
  35. J

    LC circuit with air core inductor

    Hi, I was just wondering if someone could point in the right direction to find formulas to calculate the natural resonant frequency of an LC oscillator circuit that uses and air core coil rather than a metal one. Thanks :-)
  36. M

    Finding Frequency of 20mH Inductor & 30 Ohm Resistor in Parallel

    im given a a 20-mH inductor and a 30 ohm resistor in parallel. Z_in is 25 degrees. and I am asked to find the frequency omega in rad/s here's what i try to do: 25=(jw.02*30)/(jw.02+30), and solve for w, but i don't get the right answer. what is it that I am doing wrong?
  37. B

    20.0-mH inductor potential energy problem

    Inductance You are given a 20.0-mH inductor by your laboratory instructor, who then asks you to place it in series with a power supply. Before instructing you to turn on the power supply, he quizzes you on your understanding of the behavior of solenoids. a. How much magnetic potential...
  38. J

    Can anyone provide guidance on building an inductor for a hobby project?

    Hi there :) Can someone please help me with any tutorials/pdf docs/websites/formula on how to build an inductor? I need to create an inductor of 1.35mH ... but I would like it to have a reasonably large area... maybe a coil with a diameter of 20cm? And if there's any formulae or program...
  39. T

    RMS Current in Circuit with Capacitor, Inductor, Resistor, AC Source

    Four circuit elements—a capacitor, an inductor, a resistor, and an AC source—are connected together in various ways. First the capacitor is connected to the source, and the rms current is found to be 25.1 mA. The capacitor is disconnected and discharged, and then connected in series with the...
  40. T

    Understanding the Relationship Between Inductors and Resistors in an AC Circuit

    v(rt) = 125mV cos (wt + 60) R=250 ohms L = 250mH find i(t) in the circuit there is a inductor in series wif the resistor the answers i(t)=0.5 cos (wt+60) may i know why is it the inductor not using to form z and then only divide by v(rt) ??why only the resistor??
  41. M

    How much of this energy is stored in the magnetic field of the inductor?

    For the circuit of Figure 30-19, assume that EMF= 14.0 V, R = 5.40 , and L = 5.00 H. The battery is connected at time t = 0. Picture: http://www.webassign.net/hrw/hrw7_30-19.gif Okay i know there is a simple formula to find the: (a) How much energy is delivered by the battery during the...
  42. M

    How to Calculate Energy Loss in an Inductor with Internal Resistance?

    help please! I need a little help here. The question says to consider an inductor with L=16H and an internal resistance of 0.10 ohms. We wish to use this inductor to store 0.10 MJ of energy. What is the rate at which energy is lost to Joule heating in this system? It is not practical to store...
  43. P

    Magnetic field stored in an inductor?

    Does anyone know how a magnetic field stored in an inductor (like a solenoid) can be used to light a globe (when connected via a circuit)? I assume there must be a changing magnetic flux caused by a change in magnetic field in the inductor so as to induce an electric field causing a potential...
  44. C

    Capacitor voltages and Inductor currents

    I have been taught that the voltage in a capacitor and the current in an inductor cannot change instanteously. This is important especially when solving differential equations for a circuit network. Can someone explain to me why these events cannot happen? To the extent of my knowledge for these...
  45. A

    Creating a Small EMP Using an Inductor & Capacitor

    Does quickly shorting out an inductor in series with a capacitor create a small emp?
  46. L

    How to measure parasitic capacitance of inductor

    How can I get the parasitic capacitance of a inductor? I have a scope, current probe, function generator. Thank you.
  47. S

    Fermi energy contribute to the field in the inductor

    Ok, so here's the basic idea. You have a refrigerator, with four walls each 6ft x 2ft x 4in. The walls are made out of copper(high thermal conductivity), with a silicon chip at the center. This chip is connected to an inductor and is essentially a L-C oscillating circuit. As the chip heats up...
  48. W

    Inductor (and Capacitor) Discharge

    Hello folks, just having a few problems getting my head round LRC circuits and so have gone back to basics, first starting with Capacitors and Inductors discharging through resistors. At this stage I ask of you kind sirs two things: 1. Confirm that my understanding of the capacitor discharge...
  49. G

    What Happens to an Inductor When the Circuit Is Broken?

    Hi all ! I have a question regarding the behaviour of an inductor upon breaking the circuit it belongs to. Now I don't know that much about electronics (I've just started formal training in this area), so I might have gotten some things wrong. If this is the case, I would appreciate...
  50. T

    Radio Tuner without an inductor coil

    A friend and I are trying to build a radio controlled airplane, but an LCR circuit tuner would be too heavy. Does anybody know of a way to make a tuner without an inductor coil? Any help would be appreciated.
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