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. D

    Dc to AC inverter inductor calculation

    Hi all, i am working on an 110W inverter (Dc to AC) project that the input voltages varies from 700Vdc-1000Vdc and the output voltage is 220Vac. The system operates, however i have problem with output choke. The output choke temperature increases instantly even in no load operation. My...
  2. P

    LC circuit with inductor problem

    Homework Statement An LC circuit with an inductor of 4 microH is used as tuner for an FM radio. The capacitance required to tune into a radio stations of 100 MHz is most nearly what? Homework Equations w= 2pif = 1/sqrt LC The Attempt at a Solution I plugged in 4 microH into...
  3. F

    How is Energy Stored in a Magnetic Field?

    i know how can energy be stored in an object in a gravitational or electric field simply by working on the charge or mass agianst the respective field but how can energy be stored in a megnatic field i mean how would that be explained hypothatically ?
  4. A

    Current in Inductor: Calculate Voltage at 7A

    Homework Statement If the current in the inductor 10mH decreases exponentially from its initial value of 14 A with a time constant of 3 seconds, what is the voltage across the inductor at the instant when the current reaches 7 A? Homework Equations V(t)=L di/dt The Attempt at a...
  5. T

    Engineering Find Vx: Inductor Assumed to Have No Energy Stored

    Homework Statement find Vx for all t inductor assumed to have no energy stored [PLAIN]http://img651.imageshack.us/img651/773/circuitgt.jpg Homework Equations inductor v = L di/dt unit step = 1 for t>0, = 0 for t<=0 The Attempt at a Solution using node voltage...
  6. J

    Calculating Magnetic Flux in a Toroidal Inductor

    Homework Statement A 4.50 mH toroidal inductor has 125 identical equally spaced coils. 4.5 mH = .0045 H (Wb/A) N = 125 I = 11.5 A φ = ? - this is what we're finding If it carries an 11.5 A current, how much magnetic flux passes through each of its coils? Homework Equations I'm really blank...
  7. S

    Calculating values in a simple, multi-component inductor circuit

    Hi all, I'm a first time poster here, so this probably seems really audacious, but i have an assignment to do within the next 5 hours which decides whether i fail this year of college, so any help would be hugely appreciated. I'm a first year computer science undergrad in ireland (so it's...
  8. L

    Engineering A circuit comprises an inductor of 700mH of negligible resistance

    Homework Statement A circuit comprises an inductor of 700mH of negligible resistance connected in series with a 15Ω resistor and a 24V d.c. source. Calculate: a) i) the initial rate of change of current ii)the time constant (T) for the circuit b) the value of the current after 1T seconds...
  9. M

    A Bit of Help With Peak Current Flowing with Inductor Please

    Hi can somebody help me with part B of this question please? :) I already did part a) and I found the peak current to be 31.1 mA, and the power rating required to be 4.84 W. For part B I know the current for inductance is I=(1/L)\intVdt and I know V=V0sin(wt), however with only this...
  10. M

    Shortening pulses with an inductor

    Hi everyone, quick question - I have been using a pulsed driver to pulse an LED. By placing an inductor in parallel with the LED, I can shorten the duration of the pulses from the LED. I'm looking for an explanation as to why this is the case... I'm guessing that the inductor act as a...
  11. T

    What is the current through the inductor as a function of time?

    Homework Statement A current pulse is fed to the partial circuit shown in Figure P32.20. The current begins at zero, becomes 10.0A between t=0 and t= 200microseconds and then is zero once again. Determine the current in the inductor as a function of time. Homework Equations I=...
  12. S

    AC with INDUCTOR IMP DOUBT

    What i know the most fundamental thing is that the emf supplies energy to the charges and these charges have to reach the other end(say for electrons to reach the + end). IN order to do that somehow or the other they have to drop their voltage or energy for this to happen . AC with inductor...
  13. Z

    Why is the induced EMF on an inductor equal to -L (di/dt)?

    so the amount of work done to drive the current through the inductor is given by dw=Eidt where E is the emf of the variable voltage source.We put E=+L (di/dt). can you please tell me why we put that value?? (i know the induced e.m.f on the inductor is - L (di/dt) thanks :smile:
  14. J

    What Does the Voltmeter Read When a Current Increases in an Inductor Loop?

    Reading a different homework problem here made me realize I don't understand somethings about inductors. I made a simple problem that focuses just on the inductor to help me learn. Please do help me solve this problem. Homework Statement Consider this: The loop has inductance L, no...
  15. E

    Sign of voltage across inductor

    I need help understanding the sign of voltages across an inductor. Homework Statement There is a current source providing current I to a resitor of resistance R in series with an inductor of inductance L, of which the other end is grounded. The voltage at the current source is V1 and the...
  16. L

    How Do You Calculate the Total Charge in a Solenoid with Time-varying EMF?

    Homework Statement A selfinduced emf in a solenoid of inductance L changes in time as E = E.e^-kt. Find the total charge that passes through the solenoid, assuming the charge is finite. Homework Equations E = LdI/dt U = 1/2LI^2 I = dQ/dt The Attempt at a Solution I'm pretty...
  17. B

    What is the equation for the impedance of an inductor in a Wheatstone bridge?

    Homework Statement Two inductive elements that are wired into a Wheatstone bridge. Upon displacement of the sensor, each inductor will change by delta L one increasing, the other reducing. What is the equation for the impedance of an inductor? Determine an expression for the ratio of the...
  18. B

    Understanding Inductors and Transformers

    I've been reading up on inductor and transformer design, and was interested to read the following: "Ideal magnetic materials cannot store energy, and practical magnetic materials store very little energy, most of which ends up as loss." So if I'm understanding this correctly, a big 10 Henry...
  19. R

    How to get the Q of my inductor

    Hello, I'm trying to construct a simple Class A Common emitter Colpitts oscillator. The Electronics book that I have tells me that I need to compute the Rcoil of the inductor. To do that, I need the Q factor of the inductor at 1 MHz, which is the frequency I'm trying to generate. How do I get...
  20. Z

    Balance condition for inductor bridge

    1. A Wheat stone bridge resembling setup is given with two parallel branches , the 1st containing an Inductor of Inductance L1 and resistance R1 in series with a resistor R2. The second branch consists of inductor with inductance L2 and resistance R3 in series with a resistor R4. The branches...
  21. P

    Winding your own air-core inductor

    I am trying to duplicate an already existing inductor by buying the components and winding it myself. I have found several different sources that give me different equations for determining inductance. My questions are as follow: - What is the governing equation for determining the inductance...
  22. B

    Solving Circuit with Large Resistor and Inductor: Q = CV?

    Homework Statement Hello: I've this circuit: -----Resistor (100000 ohms)---/ (switch) ------- | | |A Battery Capacitor Inductor | |...
  23. M

    Inductor or Ballast: What Does Choke Mean?

    hi there i just need to know , we use ballast of fluorescent lamp or ( inductor) in series ,i know it chokes the current ,so i just need to know what that choke means,does it increase the value of current ( means to say does it increase the charge transfer per unit time) or does it means it...
  24. R

    Calculating wire lenght for an air core inductor

    I would like to build an air coil that will create a flux field, which will in turn induce a closed loop coil, that results in an equal and opposite force. The power source is an array of PV cells hooked up in series or parallel which ever will give the air coil the greatest/strongest magnetic...
  25. B

    Insulated inductor vs non insulated

    Im wondering what the difference would be for an inductor made of insulated copper wire and one without insulation in its effect of producing a magnetic field. Are there any cases when one would be used in place of the other?
  26. M

    What is the length of the inductor?

    Homework Statement A 0.5533 mH inductor has a length that is four times its diameter. If it is wound with 15.4 cm−1 turns per centimeter, what is its length? Answer in units of m. Homework Equations L= (Uo*pi*r^2*N^2)/(l) N= n*l length=4*diameter therefore l= 2*r The Attempt...
  27. P

    Understanding Inductor Voltage at 9uSeconds in Electrical Engineering

    Ok, this was not a homework problem, but a question I had on a test for electrical engineering. The question was as follows; "What is the inductor voltage at 9uSeconds." Ok, the way I approached the problem, and was marked as being wrong. I said that I know the equation for an inductor is...
  28. J

    Difference between an inductor and a solenoid

    I've just recently seen the term "inductor" for the first time and it kind of threw me off. I'm just wondering, what's the difference between an inductor and a solenoid, if there is one?
  29. X

    Inductor Burning: Low Voltage Causes & Explanation

    Is it true that when a lower voltage is applied across an inductor it burns up the coil? If so can someone please explain why?
  30. G

    Solving Inductor 12 Henry Discharge: R Calculations

    Homework Statement Inductor 12 Henry, energy supply is Emf knot. At t=0, the switch is opened which leads to rapid discharge along a resistor. The flash from the discharge lasted 50 ms. What is the resistance of the resistor? Homework Equations I know to use i=Ie^(-R/L) t but what...
  31. C

    RLC Circuit - Voltage drop across Inductor

    Homework Statement A 10 μF capacitor and a 25 H inductor are connected in series with a 60 Hz source whose rms output is 112 V. Find the voltage drop across the inductor. Answer in units of V. Note: Sigfigs do not matter Homework Equations I = V/Z where Z is the impedence XL =...
  32. B

    Power in a circuit with an inductor and integrals

    1. The power into a circuit element in the product of the voltage across the element and the current through the element. Assuming a voltage v(t) = V_p cos(omega*t) across inductor L, integrate the power over one cycle and show that the net energy into the inductor is zero. V_p is the peak...
  33. V

    Varnish or Potting, Which one is Better to Avoid Humming Noise from Inductor

    Someone just tell me that, "varnishing an inductor can reduce humming noise much better than encupsulating it", and this is what his friend told him where his friend worked in power supply field for over 10years. (But I don't know did his "encupsulating" means potting) Or did he mean varnish...
  34. T

    Magnetostatics - magnetic flux and energy in toroidal inductor

    Homework Statement A toroidal inductor consists of 500 turns of wire on a ring-shaped core of magnetic material with a relative permeability of 8000. The core has a square cross-section with an internal radius of 20mm, external radius of 40mm and height of 20mm. Find: a) Magnetic flux in the...
  35. F

    How Does Ohm's Law Apply to an Inductor in a DC Circuit?

    The resistance of a 4 H inductor is 50.0 Ω. The inductor is suddenly connected to a 5.00 V cell. What is the final steady current in the circuit? I have no idea where to start with this. Can someone point me in the right direction please? Thank you.
  36. Phrak

    Inductor and Transformer Design Equations

    I thought it would be a good idea to write this down, all in one place, finally. Any errors, or impovements needed? Should it be in gaussian units?
  37. X

    Archived Q about derivation of formula for current in AC with inductor

    Homework Statement I'm reading fishbane's physics textbook right now, and in his derivation for I(t) in an AC circuit with an inductor, he does: Vsin (wt) - L dI/dt = 0 (kirchoff's rule, V = voltage amplitude in the AC circuit, L = inductance) then to find I, I= integral of (V/L...
  38. X

    Finding the Inductor in an RL Circuit

    Homework Statement I'm trying to find the inductor RL Circuit: Resistor (22Ω), Inductor , Function Generator Resistance (Ω): 24.7 Ω 50 RL Circuit Half-Life: 64.00µs RLC Circuit, Resonance: Resistor (1000Ω), Inductor , Function Generator...
  39. P

    RCL circuit containing only a capacitor, inductor, and generator

    Homework Statement A series RCL circuit contains only a capacitor (C = 8.46 μF), an inductor (L = 6.01 mH), and a generator (peak voltage = 77.4 V, frequency = 2.45 x 103 Hz). When t = 0 s, the instantaneous value of the voltage is zero, and it rises to a maximum one-quarter of a period later...
  40. S

    Capacitor and Inductor in Parallel

    Homework Statement How do I combine these into an equivalent impedence? I'm dealing with complex impedence, but I'm not sure how to make them into an equivalent impedence. Homework Equations The Attempt at a Solution I guess Zeq= 1/[(1/Zc)+(1/ZL)]. Is this right?
  41. N

    Power dissipated in the inductor

    In RL, AC circuit, an AC source vst = 220sin(40000t-45°) is connected to a 60mH inductor and a 3kΩ resistor. Show that the power dissipated in the inductor is zero. The current in this circuit is 0.057A as I calclulated. I know that inductor has no charging role in this circuit. But...
  42. D

    Understanding the Q-Factor of Inductors in Resonant Systems

    Hi all, For a resonant system, there is usually a transfer of energy into another kind of energy back an forth (kinetic to potential; electric to magnetic, etc). for an LC tank or an RLC circuit, we know that the energy is transferred from as an electric field between the capacitor's plate to...
  43. P

    DC voltage across the inductor?

    what happens when u apply DC voltage across the inductor? i.e is the voltage drop only across the series internal resistance of the coil? can we just determine this resistance by simply saying: V_supply = I x r(series)? or do we have to include the inductance?
  44. F

    Optimizing Inductor Center Tap Placement

    What determines where a center tap should be placed on an inductor or does it not matter?
  45. E

    Frequency of AC circuit with inductor

    Homework Statement The voltage across and inductor reaches its maximum value 22ms before the current supplied by the generator reaches its maximum value. What is the lowest possible frequency at which the generator operates? Homework Equations I used the equation V=V_(max)sin(wt+90)...
  46. N

    Self-inductance of an inductor - theoretical vs measurment

    Hi, I did an experiment where one of the 'questions' was to determine the self-inductance of an inductor. I am going to leave out the experimental method, but if you need to know just say so and I'll try to explain. The value I got was L = (3.910 \pm 0.009) \text{ mH}. I am fairly confident...
  47. ShawnD

    Charged inductor with no discharge path?

    Suppose I have a simple DC circuit. If I wrap the wire around a piece of iron, I create an inductor. Having a steady flow of current creates a steady magnetic field around the piece of iron. If I remove the power supply and put a wire in its place, the magnetic field will collapse and send a...
  48. I

    Instant change of current in an inductor

    Ok, here is a goofy question. Say you have an inductor that is connected in a simple DC circuit and has been there for a "long time". Now if you had a switch that you could move at any speed that you wanted to and could be any distance from the terminal that you wanted it to be what would...
  49. K

    Reactance and Inductance of an inductor

    a. The reactance of an inductor is 100 ohms at 2kHz. What is the inductance of this inductor?? b. At what frequency is the reactance of a 3.5-mH inductor equal to 10 ohm? I am not even sure what equations to use for these two questions. I know that for a the inductive reactance equation...
  50. R

    Why does the resistance of an inductor vary with frequency?

    Hi, How does an INDUCTOR AND A STRAIGHT WIRE differ?how come the resistance offered by an inductor changes with frequency??
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