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.

View More On Wikipedia.org
Recent contents Top users
  1. Asmaa Mohammad

    The induced EMF in an inductor

    Homework Statement A generator consists of 500 turns each of surface area 7/11 m² . It rotates at rate of 50 revolutions per second (f =50 Hz), in a field of magnetic flux density of 5*10^-4 T, its terminals were connected in series with a capacitor (Xc=110Ω), an inductor (Xl=80Ω) and a...
  2. D

    Shim Inductor in Phase Shifted Full Bridge topology

    What is the purpose of the shim inductor and how exactly does it function in PSFB topology? I noticed that I had dramatically improved efficiency when I added a shim inductor to my circuit, not too sure how or why this works though.
  3. A

    Inductor and bulb in an circuit

    Homework Statement the problem statement is provided in the attached file Homework Equations logic based , basic principle of inductors. The Attempt at a Solution after switch is opened the more the current passes through the bulb , more will be the brightness . earlier in the steady state ...
  4. T

    Boost converter inductor discharging question

    I'm reading up on boost converters and so far I understand that it basically uses the inductor as a source together with the actual supply voltage to boost the voltage. During the discharging period, why would the current (if allowed to) drop to zero ?, wouldn't the supply or battery still be...
  5. Asmaa Mohammad

    The potential difference across an inductor

    Homework Statement In a circuit, a capacitor (Xc=30Ω, R=44Ω) and an inductor (Xl=90Ω, R=36Ω) are connected in series with an AC source (ƒ=60Hz, V=200V). Determine: 1-current intensity 2-the voltage across every component in the circuit. Homework Equations Z=√R²+(Xl-Xc) Where: Z is the...
  6. A

    LC circuit current of inductor

    Homework Statement In the figure given, find i(t) for the inductor My problem is though when we found i(t) with a source we find the transient response and the steady state response... I know how to do the transient response of an RLC circuit not an LC one... do i just consider R to be 0...
  7. A

    Current direction after changing inductor to short circuit

    Homework Statement In the figure in the picture uploaded assume that the switch has been closed for a long time such that the inductor acts like a short circuit. Through which resistors does the current pass through and why?? Homework Equations A short circuit is basically a wire or a zero...
  8. S

    RLC Circuit with a Gyrator as an Inductor

    Hi, Im trying to build a resonant circuit with a ~low frequency resonance (<1kHz). I am using a Gyrator (https://en.wikipedia.org/wiki/Gyrator#Application:_a_simulated_inductor) as the inductor. Im using: RL = 100ohm R = 27kohm C = 1uF I put another 1uF capacitor in front of Zin, to form a...
  9. 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...
  10. cnh1995

    What Happens to Inductor Current When the Switch is Opened?

    I was thinking about the discharging mechanism of an inductor and I have a question about it. It might sound stupid to the physics experts here, but I can't help thinking about it. Before I ask my question, I want to mention a few points I already know about an inductor.. I know an inductor...
  11. 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...
  12. T

    Confused about inductor polarity

    So initially S1 and S4 are closed and current flows as seen above. After some time S1 and S4 are open and current flows as seen above. Now I am confused about the polarity of the inductor, what if I said the current flows through D1 and D4 instead of D3 and D2 ?, would that be wrong ?
  13. 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?
  14. Titan97

    Capacitor and inductor in parallel

    Homework Statement [/B] Find the power supplied by the battery. Homework Equations $$Z_C=-iX_C$$ $$Z_L=iX_L$$ The Attempt at a Solution $$Z_1=R_1-iX_C=\sqrt{R_1^2+X_C^2}e^{i\phi_1}$$ $$Z_2=R_+iX_L=\sqrt{R_2^2+X_L^2}e^{i\phi_2}$$ $$I_1(t)=\frac{V_0}{\sqrt{R_1^2+X_C^2}}e^{i(\omega...
  15. S

    Inductors and circuit problem

    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 } \\...
  16. D

    Current through an inductor after a switch closes

    Homework Statement Let's say I have a circuit such as the one above, and let's say the circuit has been open for a long time. How would I find the current through the inductor, the instant after closing the switch? and the voltage potential across the 40 mh inductor? Homework Equations...
  17. S

    Engineering Solving for i and v_x: A Homework Challenge

    Homework Statement Find i and v_x Given answer: 2. Homework Equations 3. The Attempt at a Solution I have attempted the problem in two different manners, and I consistently reach a different answer. I would appreciate if someone would be willing to take the time to attempt the problem and...
  18. 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...
  19. 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...
  20. S

    Inductor and lamp in parallel

    Trying to figure out why an inductor in parallel with a lamp and battery will cause the lamp to GRADUALLY increase in brightness to a steady glow. I understand the concept of a coil of wire, producing a changing magnetic field when the current running through it changes then the changing...
  21. 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...
  22. P

    Find the current through the inductor

    Homework Statement Find a differential equation for current through the inductor and then solve it. The battery carries voltage ##V_0## (The switch is closed at t=0s) Homework Equations ##v=\frac{q}{C}## (Capacitor) ##v=L\frac{di}{dt}## (Inductor) ##v=IR## (Resistor) The Attempt at a...
  23. I

    Just spent $20 on an inductor to be used with a $12 speaker?

    I recently replaced the rear "sub-woofer" speakers as the originals had rotted away in my vehicle. And? And it sounded terrible. Now I was getting the whole spectrum -or at least close to & the break up on the top end was nasty.What I didn't realize is that Subaru had glued an inductor on the...
  24. A

    Deriving capacitor and inductor models from Maxwell's eqs

    I'm sure the inductor model, i.e. vL(t) = iL'(t)*L follows without directly from Faraday's eq. But even there, with Faraday's equation we think of the changing magnetic field as inducing the voltage in the loop, where in the model it seems the other way around, that is, the voltage increases...
  25. 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...
  26. N

    Why did they use only meter resistance for tau of inductor

    Homework Statement http://imgur.com/uLZdBJC 27. The switch has been closed for about 1 h. It is then opened at the time defined as t 0 s. a. Determine the time required for the current iL to drop to 10 μA. b. Find the voltage VL at t 10μs c. Calculate VL at t 5tau. Homework Equations So I...
  27. L

    What are the effects of eddy currents in an inductor core?

    I've been googling around, and I can't seem to find a straight answer to this: Do eddy currents generated within an inductor core change the inductance, the impedance, or both? My reason for asking is to understand whether more or less eddy currents will change the resonant peak of the...
  28. L

    A couple Q's about parasitic capacitance in an inductor

    First question; I was measuring capacitance in various guitar pickup coils that have the same diameter of wire with an Extech LCR Meter, and it seemed to be that the more winds, the higher the inductance as expected, but I would get lower capacitance readings, too, both at 120 kHZ and 1k Hz...
  29. F

    Polarity of back EMF in an inductor....

    Hello Forum, the law of electromagnetic induction states that a time-changing current causes a back (counter) emf in an inductor. The back emf opposes the change in current by generating an induced current I_ind. If dI/dt>0, the induced current is opposite in direction to the main changing...
  30. R

    Finding Zero Power at Inductor Terminals

    Homework Statement Find the time, greater than zero, when the power at the terminals of the inductor is zero. i(t) = .20e-500t + .1e-2000t A v(t) = -5e-500t-10e2000t V L = .050 H v( Homework Equations P=VI The Attempt at a Solution It seems to me to be impossible to find a finite time to enter...
  31. M

    Inductor behavior connected directly to DC (no resistor)?

    If an ideal inductor is connected directly (no resistor present) to a DC voltage source, why does it behave like a short-circuit at time t=0? If voltage across an inductor is related to the change in current (i.e. di/dt), then shouldn't the voltage across the inductor be very large at time t=0...
  32. N

    Percentage of external B field absorbed by inductor?

    Hey all, if a magnetic field source is at A and an inductor is at B halfway from C, the measuring point will the field be attenuated and decrease in strength due to a percentage of it being absorbed by a solenoid if so how would one calculate the amount, I found how to calculate energy in an...
  33. S

    Engineering Initial and final values for second order circuits

    Homework Statement I am attempting to understand this example shown below: Homework Equations During stead state DC, the capacitor is an open circuit and the inductor is short circuited. The Attempt at a Solution [/B] The questions I have are really related to the concepts as I don't...
  34. X

    2 Port analysis of series Inductor (Simple)

    EDIT: Oops! I posted this in the wrong section! Meant to post in engineering section! I am not sure if I am doing this problem correctly or not. It is very simple. 1. Homework Statement A 2 port network consists of just a series inductor with ##Z=j 100 \Omega## in a ##50 \Omega## system...
  35. T

    Model an Inductor: Flux Through Core & Air Around It

    Hi, I'm just curious why we model the ideal inductor as having the leakage inductance as being in series with the ideal core, rather than in parallel to it? Because it would seem to me that the flux goes in two parallel directions, one through the core, and one through the air around the core...
  36. G

    Where does energy of the inductor go?

    Hello. Let's say lossless case where AC voltage source connects to inductor in series. As current increases, energy is stored in form of magnetic field within the inductor. When current decreases, stored energy is released. Question is where this energy goes? Since there is no load and system...
  37. M

    How would you explain self-induced voltage in an inductor?

    Consider the following: You have a circuit with an inductor and a battery. You have an open switch, that was open for gazillion years. The inductor is "uncharged", meaning has no stored magnetic field. Then, you close the switch. At time t=0+, right at the moment you closed the switch, the...
  38. E

    Changing core for an inductor

    Suppose you have a pure DC supply with a constant current to an inductor. And you change the core of the inductor from air to iron, leaving the current remain the same. You may try changing to other materials. Does the voltage drop across the inductor will remain the same for any core? Anyone...
  39. R

    AC Homework: 10 Ohms Resistor, 12 uF Capacitor, 28 mH Inductor

    Homework Statement A 10 ohms resistor, a 12 microFarad capacitor and a 28 mH inductor are connected in series with a 170 V generator. A.) At what frequency is the rms current maximum? B.) What is the maximum value of the rms current? Homework Equations A.) Fo = 1 / 2pi sqrtLC b.) Irms = Vrms...
  40. V

    Inductor response to applied voltage

    I'm having a bit of trouble wrapping my head around why inductors behave the way they do in certain circuits. Every physical explanation for why ##V = -L\frac{dI}{dt}## that I've seen explains how the voltage across the inductor is developed as the current changes: the changing current means a...
  41. cnh1995

    How Does Increasing Core Permeability Affect an RL Circuit's Performance?

    In an RC dc circuit at steady state, if the permitivitty of the capacitor is increased by inserting a different dielectric, additional charging current will flow and the capacitor will accept more charge (due to increase in capacitance). What will happen if the inductance in an RL circuit is...
  42. magnetpedro

    U-Shaped Ferrite Core Inductor question

    I'm using a U-Shaped Ferrite Core with coils in both legs of the U. I've calculated it's inductance using an analogy between electric/magnetic circuits. L = N2/Rtotal where: N = number of turns of coil in both legs of the U; Rtotal is the total reluctance of my circuit = R1 + R2 R1 =...
  43. smruti

    What is the difference between an inductor and a transformer (or solenoid)?

    what is the difference between inductor and a transformer...or a solenoid and a transformer
  44. kelvin490

    Understanding Inductor Behavior in Transformers: Voltage and Current Phasing

    In an inductor, a current waveform 90o out of phase with the voltage waveform creates a condition where power is alternately absorbed and returned to the circuit by the inductor. If the inductor is perfect (no wire resistance, no magnetic core losses, etc.), it will dissipate zero power. I...
  45. kelvin490

    Charge accumulated at two ends of resistor/inductor?

    In a simple circuit are there any charges accumulated at two ends of resistor? There is an conservative and thus electrostatic electric field and potential difference across the resistor. It seems it is only possible if positive and negative charges are accumulated at two ends to provide the...
  46. cnh1995

    How does an inductor determine the applied voltage in an RL circuit?

    If the switch in an RL dc circuit is closed at t=0, the current i in the inductor rises exponentially. But at t=0, i=0 because the inductor generates a back emf equal to the applied voltage at t=0. So in absence of any current,how does the inductor come to know that the switch has been closed...
  47. R

    Engineering Where is the bandpass filter in this circuit?

    Homework Statement I am doing a project on the Elenco AM/FM superheterodyne radio kit. I have been stuck for ages trying to figure out how the two common emitter amplifiers are tuned to filter out anything that is not around 455 kHz. I tried to find a bandpass filter, or a high-pass and a...
  48. P

    Find resistance of inductor in series RLC circuit

    Homework Statement We have a resistor of 350 Ohm, an inductor of 0.15H and a capacitor of 10 microfarad, connected in series to an AC source of voltage 240 V and frequency 50 Hz. The measured effective voltage over the resistor is 180V, and over the system of the both the inductor and the...
  49. S

    Understanding Inductor Behavior in a Changing RL Circuit

    Imagine simple RL circuit connected to a battery source. Let's assume that we are decreasing the resistor value linearly in a constant steady rate. This will make the current being increased linearly. Thus the current will be increasing in an inductor and it will cause a voltage to build up...
  50. jlefevre76

    Understanding the Physics of a Coilgun: A Beginner's Guide

    Hey, I've seen a few posts on this without any responses I really thought helped (at least help answer my question). So, I was hoping somebody on the forums here could help walk me through the basic physics of a coilgun. Basically, how could you characterize the magnetic field inside the...
Back
Top