Inductors and Inductance

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 thoughts on “Inductors and Inductance

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  • 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 .

  • 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)?

  • 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?

  • Почему под индуктивностью в переводе понимают катушку индуктивности?

  • 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.

  • 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.

  • 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.

  • 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

  • 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.

  • 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.

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

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  • 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.

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

  • 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?

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

  • 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).

  • 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.

  • Now I understand why a fan keeps running for a while after it is switched off. The left over electricity and magnetic energy has to be spent.

  • I now understand transient analysis fully after watching your video..!! Thank you for this great video! But can you please tell me what would happen if a resistor and an inductor is connected in parallel to a voltage source? How would then the curreny and voltage vary ?

  • This one confused me. The bar within the coil is not connected to anything. So the current flow going 'around' it is simply passing through the wire-coil which surrounds it. I thought an inductor would take the charge from the magnetic field of that coil and pass it to something, but as I said, there is nothing hooked up to that bar. And using height to represent (I guess) different voltage potentials doesn't help.

  • Did anybody else feel like they were waiting for the slowest kid in class to finalllllllly catch on so the teacher would get on with the next part? Like all through the video….

  • I wish there was a circuit simulation program that represented circuits exactly the way these videos do! What a great learning tool!

  • Such a clear explanation but cannot abide horrid pro establishment classical music. It's ruined the whole show for me.

  • What if you replaced the resistor with a high voltage capacitor? Would this charge the capacitor really fast because the resistance is so high?
    Edit: And if you put a diode in the direction of the current between the capacitor and the inductor would this make the inductor mad?

  • This is what creates the fire (spark) part of the 3 basics for combustion engine operation.
    Air
    Fuel
    Fire
    Old school was the magneto, then we got the ignition coil with plug wires.
    Now we have ignition coils on each plug in modern cars.
    Each coil ramps a 12V supply, up to 40,000V output to each spark plug, & does this repeatedly multiple times per second. The speed of repetition per second is dependant on engine RPM, & is controlled through a gated signal wire by the car's ECU (computer).YES, thats 40,000V
    Crazy, Right?

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