What is electromagnetic induction?

Answer 1

Electromagnetic induction is the idea that a magnetic field or magnetic flux that changes over time can actually produce (induce) an electric field.

Let's say that you a loop or a ring of metal wire. The loop doesn't have a battery or anything, but it's a closed loop and can conduct electricity, and the loop has an area. Now you also have a bar magnet, which produces a magnetic field. You point the magnetic field (say, the north pole) at the loop of wire. We can now measure the magnetic flux, which basically tells us how much of the magnetic field goes through the loop.

Now that you've established a constant magnetic flux, let's say that you decide to change the flux over some time period. You can either move the bar magnet towards the ring (increasing the strength of the magnetic field) or you can rotate the loop, so that less magnetic field goes through the loop. There's a few other ways, but these are just examples. Essentially, you've changed the magnetic flux that goes through the ring. If you were to do this experiment in real life, what you'd notice is that there's a current that starts to go through the ring, even though there's no battery. This current can only exist due to a voltage/potential difference, which we can also express as an electric field. What this means is that you changed the magnetic flux of the ring, and this produced a current, or electric field.

Electromagnetic induction, then, is the phenomenon that a changing magnetic flux (over a period of time) will induce an electric field or voltage inside the loop. This experiment was done by Michael Faraday in about 1831, and showed a fundamental coupling of the electric field with the magnetic field, hence the name electromagnetism.