# I have a question about the working of an inductor..

The inductor develops magnetic field around it to store the kinetic energy of the electrons into magnetic field, but i don't have a clue why does it opposes the change of current passing through it and how .. i know the Lenz's law but don't know the physics behind that..

• It's because it's storing energy, think about kinetic energy, if you want to stop, all that energy has to go somewhere, it doesn't want to stop easily, it wants to keep going. The flow of current in the inductor is exactly the same, you don't need any physics here, just a thought experiment, when something's moving, it want's to keep moving, or more precisely, it want's to stay as it was before, heavy rock wants to sit there, car rolling down hill wants to keep going. The direction and magnitude isn't important, things just want to stay as they are – Sam May 5 '16 at 7:10

The opposition to change in current is observed because the inductor is extracting power from the current and storing it as energy in the magnetic field.

So, if the current is increasing, the magnetic field will build up (which takes energy). This energy must come from the current and is extracted by causing a positive voltage across the inductor.

• Key point, it's not the kinetic energy of the electrons that's transferred, it's their electrical potential energy. – The Photon May 5 '16 at 3:58

If I wanted to store some mechanical energy I could push a rock to the top of a hill. Easy to do? No, because the rock fights all the way until I stop pushing.

If you want to take energy out of one system and put it somewhere else, of course there's "opposition". You don't get energy for free.

Natural systems tend to not like change, they want to keep equilibrium. An inductor is a classic example of a natural phenomenon which is this way. An inductor wants to keep the current steady so when the current changes it fights to slow the change by developing a voltage in opposition to the amount of change. If you want to fully understand electro-magnetics, study Maxwell's Equations which are the set of 4 equations that describe most of what you need to know.

• yes thanks buddy. i got your point and yes i read them 5 hours ago.. and i am satisfied now. thanks.. – Jigar Agrawal May 7 '16 at 1:56

The opposition to change in current is because the magnetic field built up is at a right angle to the current. This magnetic field, being at a right angle, imposes a current in the windings that tries to make the current flow at a right angle in the core (ferrite or silicon steel), instead of a smooth flow. This is sometimes called an 'eddy' current. It creates a resistance to the current your want to drive the inductor or transformer with.

It is at a right angle to the normal current flow and can lower the effectiveness of a transformer or inductor a lot. To compensate for this most all power transformers made of silicon steel are done in thin layers lacquered together. The coating keeps current from flowing at right angles while allowing the magnetic field to work normally.

Ferrite cores for switching power supplies spread the windings evenly as possible around the core if it is a toroid. If it is an 'E' core type a small .010" gap can be inserted between the 2 'E' shaped halves to lower eddy currents and prevent core saturation at high power levels.

Whether it is an inductor or a transformer the same rules apply because they are both subject to the same problems.

• @AugustCrawl. You want to play that game-be my guest. Just remember that all questions, answers, votes and comments are recorded for the Community to see. – Sparky256 Mar 5 '18 at 5:07
• I just wanted you to explain to me why my answer was bad rather than repeatedly writing "This does not answer the OP's question" so that I can write a better answer. If parts of my answer are wrong then please tell me so I can change them. If parts of my answer are unclear, then please tell me so I can address the parts of the question that I have missed! – AugustCrawl Mar 5 '18 at 5:27
• @AugustCrawl. Did you not read the comments posted to you by others? Did you look at the answers that were up-voted to see why they were? You missed the fine details. It was all about current limiting, of which you mentioned nothing. It was actually not about the voltage. – Sparky256 Mar 5 '18 at 5:31
• Ok I have added a comment about the current limiting nature of the very short time period. Thank you for specific feedback :) – AugustCrawl Mar 5 '18 at 5:40
• @AugustCrawl. This place has few rules, but 'be nice' is one of them. We help each other in spite of competition for rep points. Read the fine details of the questions and comments before posting an answer. Even the best of us sometimes get down-voted because of details we missed. – Sparky256 Mar 5 '18 at 5:54