Inductors and Inductance


An inductor is a coil of wire wrapped around a magnetic material. Current flowing through the inductor creates a magnetic field, and magnetic fields do not like to change. As a result, an inductor is a device which tries to prevent the current flowing through it from changing. If the amount of current flowing through the inductor is constant, the inductor will be happy, and it will not generate any forces on the charged particles flowing through it. In this case, the inductor behaves just like a normal wire. On the other hand, if we try to interrupt the current flowing through the inductor, the inductor will generate a force, trying to keep the current flowing through it. If an inductor is connected to itself, and there is no resistance in the circuit, the current will theoretically continue circulating forever. However, unless we are using superconductors, all wires have some resistance to them, and the current will eventually decay to zero. The larger the resistance, the faster the current will decay. But, the larger the inductance of the inductor, the slower the current will decay. Once the current is at zero, the inductor will want to keep the current at zero, due to the fact that an inductor tries to prevent the current flowing through it from changing. Therefore, when we connect this inductor to a circuit, the inductor will initially create a force trying to prevent the current through it from increasing. But, the current will slowly increase. The larger the inductance of the inductor, the slower the increase in current will be. After the current has stopped increasing and has reached a steady value, the inductor will then again be happy, and not generate any forces. But, when we try to turn off the current flowing through the inductor, the inductor will then generate a force to try to keep the current flowing through it at this new constant value. If the inductor is then connected to a resistor, the voltage across the resistor will be the current multiplied by the resistor’s resistance. The inductor prevents the current flowing through it from changing instantaneously. Therefore, the current flowing through the inductor immediately after we flip the switch will be exactly equal to what the current was before we flipped the switch, regardless of what the value of the resistor is. If the value of the resistor is extremely large, then the current multiplied by the resistance will also be extremely large. As a result, inductors can generate extremely high voltages, at least for a brief period of time. Since the current through an inductor can not change instantaneously, when we try to disconnect an inductor from a circuit, we always need to provide a path for the inductor’s current to flow. If we do not provide a path, the inductor’s current will find its own path, such as through the air, through the open switch, or through other components that are not supposed to be conducting electricity. This can create very large voltages, and cause considerable damage to the circuit. The ability of an inductor to create large voltages makes them very useful in the design of power supplies. But, this ability also means that care must be taken to ensure that we never try to switch off an inductor, without providing a path for its current to flow in. Much more detailed information about electric circuits is available in the other videos on this channel, and please subscribe for notifications when new videos are ready.

100 Replies to “Inductors and Inductance”

  1. You can help translate this video by adding subtitles in other languages. To add a translation, click on the following link:

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  2. Ghntaa…pehle toh ye smjhao mjh ye jo magnetic material h bich m wire k…prctcly ye isse chipka hua rehta hoga na toh isme ase hwa m kse dikha rkha h??

  3. I tell my students that an inductor is a bit like a paddle wheel hooked up to a flywheel, once you get the current flowing and the paddle wheel is turning the flywheel at speed, then it is going to be a bit like water hammer if you try to stop the current flow suddenly, which is what we see with the voltage spike……the flywheel analogy allows me then to show how on an alternating current system with the inertia of the flywheel effect, causes the current to be out of phase with the voltage or applied pressure by 90 degrees so the flow lags the pressure by 90 degrees….. It then leads into the capacitor adding a springiness effect to the current, which when put with the inductor allows for very quick realization of how resonance can occur. The dark art of electrical 🙂

  4. I think instead of saying an inductor is a coil of wire wrapped around a magnetic material, you should of just stuck with an inductor is simply a coil of wire since some inductors have air cores. Also would have been great to go into more detail, like not math wise but just in general the physics behind it. Great example otherwise.

  5. The first sentence is wrong. An inductor is an electrical conductor, not only a coil of wire with a magnetic core.

  6. Feelings! Everything has feelings and I'm sick of it. I'm an engineer I don't know what to do with feelings. Furthermore I don't care about the feelings of the circuits I create, they will do what I tell them to do without complaint. If they complain, I rip them from the circuit and install components that don't complain. But this explanation of how inductance behaves in a DC circuit is accurate if you can get past the anthropomorphism.

  7. Inductor is like a lady, she rejects at first but then says yes, and then if she says yes and do all you want to do with her, don't say no, or she will exert a force on you. 😀

  8. Where do you allow the current to flow when closed in a circuit without power being generated is it strictly for power storage or is it also a amplifier?

  9. Un inductor es un dispositivo que tiende a oponerse a cualquier cambio de corriente
    1 en el instante en que conectes una bateria a los bordes del inductor un flujo magnético empezara a crecer por donde la corriente vaya fluyendo esto hace que estas lineas magneticas que va incrementándose de dentro hacia afuera choquen con las espirales vecinas de la misma bobina y todos sabemos que ocurre cuando eso pasa, se induce una corriente electrica pero ahora en sentido contrarió "chocando" con la corriente que fluye normalmente esto impide que la corriente electrica se incremente instantaneamente hasta que el campo se estabilize y no corte ninguna espira
    2 al desconectar la bateria el inductor se opone a que la corriente caiga a cero abruptamente ya que al desconectar la bateria ahora el campo magnético disminulle pero ahora de afuera para adentro al disminuir va cortando las espiras haciendo que se induzca una corriente de sentido contrario ala inducida anteriormente esto hace que sigue circulando hasta que el campo magnético sea cero

  10. صراحة أحببت الطريقة التفاعلية للشرح…..
    حقا كان هذا المقطع مفيدا و رائعا …..
    استمر يا صاحب القناة فأنت تقوم بعمل رائع….

  11. the use of inductors is prevalent in AC circuits, u didnt do anyone any favors in leaving out collapsing and expanding magnetic fields and counter emf, i am glad i knew how they work before watching this…

  12. how could you say that the inductor gives force … according to me, it is the only way for the electron to travel … there is no force exerted by the inductor .

  13. How would be the current flowing through the inductor will be same before and after the switch is flipped as some electrons left on the first part of the circuit (left to the inductor)?

  14. How the current in the inductor will be same before and after the switch is flipped as some electrons left on the left side of the inductor?

  15. Почему под индуктивностью в переводе понимают катушку индуктивности?

  16. WOW, I just found this video and your channel, it's amazing! The combination of animations, music, narration and the tempo makes is so pleasant to watch while still being learnful. I don't understand why I never found your video's before and why you don't have more views and subcribers, you deserve them.

  17. 1:20 По замкнутой катушке, течёт ток ? Ну Вы даёте.👍😉

  18. Hello Eugene, your videos are very well put together and are informative. I work at the Conservatory of Arts and Sciences in Gilbert AZ. I have shown a couple of my students the videos of series and parallel circuits, as we do teach a bit of Ohm's Law and Kirchoff's Law of Current. I was hoping to receive your permission to pass on the links from YouTube. We will typically include a link in our iBooks and then direct them to different sites for further study material. All in all our goal is not concentrated on the performance of music, but the recording and implementation into various technical fields within the recording and live concert sound industry. Thank you for your consideration. Please feel free to contact me at [email protected] Thank you for your time, James M. Bender, Instructor.

  19. Small correction, an inductor does not need a magnetic core (first statement), infact, any conductor has some inductance, its only really noticeable to high freq circuits.

  20. Magnetic field have inertia, so ehm ehm, i state second law of motion in electric domain… Rate of change of magnetic field is directly proportional to the voltage applied, and the change(current) is in the direction of voltage applied

  21. I love these videos they are so Classical
    and Unique, like what a German WW2 Scientist
    would make 😂😂😂

  22. The background music is such a nuisance. For this lecture, it needs a quiet thinking environment because the status of an inductor or capacitor is a ever changing thing during working with AC. The narrator speaks in a very slow pace which is helpful for a listener to think her speeches. But the background noises spoil all good things, especially its volumes go up one second and down the next.

  23. Минуты достаточно. Постоянное магнитное поле возникающее в сердечнике и есть та индуктивность. А в переменном токе магнитному полю приходится постоянно меняться и оно мешает току . Назовите индуктивность магнитным полем сердечника и всё станет ясно.

  24. Every wire has a small resistance to them. Then does the resistance value increase if we make the wire longer ?

  25. To see subtitles in other languages: Click on the gear symbol under the video, then click on "subtitles." Then select the language (You may need to scroll up and down to see all the languages available).
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  26. So … the circuit behaviour is governed by the 'happiness' or 'unhappiness' of an inanimate object??? Better to just say that for the inductor, a changing current always occurs at the same time as a voltage. Great explanation otherwise, and nice graphics.

  27. amazing videos! helped me understand the concepts very easily.
    keep up the good work guys.
    your channel is a great help for the students.

  28. Don't they use this in computers to control the voltage to the CPU, GPU, or anything else in the system that requires stepping 12V down to 1.3V etc?

  29. Ну как отделаться от этой навязчивого воспоминания о рекламе колбасы, когда звучит эта музыка…

  30. I always think of an inductor as a electron turbine/pump, (mechanically) connected to a flywheel.
    The flywheel doesn't like to change it's motion (still or moving).

  31. Spoilt by the music.
    Why the music?
    What is the point of the music?
    Why introduce a distraction in this lesson?
    Do teachers play music while they are teaching you? NO.

    Shakes head and walks away.

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