induction

It hard to really try to answer, your question, I am taking for granted you understand some basic electrical engineering

how it can be said that fulx is cutted and emf is induced.

That would be line of flux that is cut and a perpendicular angle.

Lenz's law states that current is induced in such a way as to oppose the the change in flux. This is a consequence of conservation of energy.

An example of Lenz's law is that when the magnet is brought near the coil, the magnet's magnetic field cuts through the coil increases, and therefore the flux increases.

The field from the magnet is not uniform--but it's stronger the closer you get to the end of the magnet. So when you bring the magnet closer to the loop, the field through the loop is stronger.

Having the current oppose the change means that it takes work (a force pushing through a distance) to create that induced current. If it didn't, we could get free current! (That's not going to happen.)

The magnetic field of the magnet points upward. To oppose the upward increase, the magnetic field inside the coil produced by the induced current needs to point downward.

When the magnet is brought far away from the coil, the flux decreases, so the induced current in the coil produces an upward magnetic field through the coil that is trying to maintain the status quo, ie keep things in check.

Think of the induced current as a response to the changing flux within the loop due to the movement of the magnet. The induced current will be in such a direction as to create a secondary field that opposes the change in flux.

p911

I never got very good at the heavy math, and I have lost a lot of what I had. But, I think that there is another "twist to understanding" that might be added. Everyone talks about "lines" and I always wanted to know why the lines were there and how they were created. When I asked questions I would sooner or later always get a reference back to the iron powder creating "lines" when sprinkled on paper over a magnet. That was proof that "lines" were right. Well, I still don't "fundamentally" believe it.

For the magnet issue: I think that the magnetic permeability of the iron powder pulls in the magnetic field and creates little iron powder magnets with local areas of disturbed (reduced?) magnetic field around them. The magnetic field and the first little iron powder magnet help another spec of iron powder to become a small magnet and their opposite poles are attracted. Do this over and over and you have what looks like a line created by the iron powder. In the area beyond this "line" the magnetic field will cause all this to happen again, and beyond this ... again and again.

Due to advanced math-a-magics the "lines" of iron powder will be closer together if the magnetic field is stronger and farther apart if the magnetic field is weaker. Thus, iron powder and paper is a lot like the output of an advanced computer program. In both cases, the closer together the lines are the stronger the field.

So far it might seem like I am in disagreement with phoenix991, or it might seem like I am in agreement, or it might seem like I have gone too long without a good nights sleep. I hope phoenix911 or someone else with more knowledge than me will reply because I think that I am in agreement but taking it one step further. And the reason I am doing this is because I also have a problem with cutting lines and therefore induction.

My theory is that many times "lines" are not actually "cut", but by viewing the iron powder lines before the coil is moved into them and thinking about the coil "cutting the lines" then we will have a good "human feel" for the magnitude of the field strength that is disturbed by the moving conductor (or moving field and stationary conductor).

I think that "lines" are only cut on paper and that in free space the fields are disturbed (and therefore energy/electromotive forces are induced).

bruceflorida

what is magnetism is a good question. This explains a little about magnetism. But not the force itself.

But one can look at these "lines" as "paths" if it will help. What what does it consist of? Can't help you with that.

Off on a tangent a little. About material being magnetized its basically about the atoms being lined up in position. This can be broken or disrupted by shock. i.e. dropping a magnet and it loses it magnetism.

On the other hand, this can be an interest experiment, and can also help you. Take a ferritic rod and have a loose grip on it and strike it linearly (i.e. hold it straight up/down and strike it down) against a solid object. That rod will temporary be magnetised. )This can work with screwdrivers.

I had came home to the farm from college we were working on our well and my brother dropped a screwdriver in an open type pit. Was not enough room to reach it.

We had some neighbors that had stopped by watching us work, giving us opinions on how we should have done it.

Well, we had a crow bar near (about 6' and 1 to 1 3/4" dia. and weight i don't know 30 lbs maybe), I grabbed it and struck it against a rock.

They got spooked by the sound and said what the hell and watched, They thought I was pissed or something, but I got their attention. My brother had a half smile, he knew I was up to something. Well keeping a straight and profession face they watched as I lowered the crowbar and you should have seen the look on their faces when we heard a slight ping, I raised it, and low and behold, the screwdriver was barely hanging on the end, but hanging on.

They asked how in the hell. My reply, "Magic I guess.......or physics". Which opened up alot of conversations from my brother such as working smarter not harder and such.

I don't have flash on this computer. I'll take a look at the link tomorrow.

Thanks,

Bruce