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Lenz's Law
I understand that when you move the north pole of a magnet towards a loop of wire, it induces a current in that loop, and that the current makes the end of the loop facing the magnet have a north polarity so that it repels the magnet. Does this mean that the currents direction is towards the north end of the loop due to the right hand grip/ cork screw rule? If so, when the magnet moves away from the loop and the end of the loop facing the magnet changes to south polarity, does that mean that the current has changed dirrection, and is now moving backwards to how it first was moving?
yes, when the magnet starts to move away from the loop, the direction of the current in the loop will change direction.
The way I like to think about lenz's law is by thinking about loops of wire hating to have their magnetic field changed, and they're going to do anything they can to avoid it happening. So when you come along with a magnet, and shove it near the end of a wire loops, you're trying to change the magnetic field through the loop from 0 to, say, some positive number (with respect to a chosen axis). The loop hates this, and so acts to generate a field to cancel this out - i.e. a negative magnetic field (with respect to the chosen axis).
So if you had the magnet on the left side of a loop, with the north pole end closest to the loop (i.e. field going from left to right), then the loop is going to generate a field going from right to left.
But when you start to move the magnet away from the loop, you're now trying to decrease the field in the loop, which the loop also hates. So now it's going to try and reinforce the field which you are taking away from it, so the current direction will flip and the field generated will go from left to right.
In your case, you are passing the magnet through the loop, I think. So what happens is the magnetic field is going up and up in the loop, so the induced field is going up and up in the negative direction. But when the magnet is half way, the field is at a maximum in the loop, and so the induced field is zero (when at a maximum, there is no local change), so no current. And when the magnet continues to move out of the loop, the current now flows in the opposite direction. I.e. the current increases in one direction, slows down to zero, and then flows in the other direction, and then slows down back to zero
The way I like to think about lenz's law is by thinking about loops of wire hating to have their magnetic field changed, and they're going to do anything they can to avoid it happening. So when you come along with a magnet, and shove it near the end of a wire loops, you're trying to change the magnetic field through the loop from 0 to, say, some positive number (with respect to a chosen axis). The loop hates this, and so acts to generate a field to cancel this out - i.e. a negative magnetic field (with respect to the chosen axis).
So if you had the magnet on the left side of a loop, with the north pole end closest to the loop (i.e. field going from left to right), then the loop is going to generate a field going from right to left.
But when you start to move the magnet away from the loop, you're now trying to decrease the field in the loop, which the loop also hates. So now it's going to try and reinforce the field which you are taking away from it, so the current direction will flip and the field generated will go from left to right.
In your case, you are passing the magnet through the loop, I think. So what happens is the magnetic field is going up and up in the loop, so the induced field is going up and up in the negative direction. But when the magnet is half way, the field is at a maximum in the loop, and so the induced field is zero (when at a maximum, there is no local change), so no current. And when the magnet continues to move out of the loop, the current now flows in the opposite direction. I.e. the current increases in one direction, slows down to zero, and then flows in the other direction, and then slows down back to zero
oh ok, that does make things a bit more clear. So will this process just keep going on and on? I mean will the loop keep repelling the magnet and attracting it over and oer again, or is there a certain time when it stops?
Also theres some things that i didnt really get in your last paragraph. You talked about the magnet going right through the loop, but i thought that as soon as it reaches the begining of the loop, it will be repelled?
Also theres some things that i didnt really get in your last paragraph. You talked about the magnet going right through the loop, but i thought that as soon as it reaches the begining of the loop, it will be repelled?
void
oh ok, that does make things a bit more clear. So will this process just keep going on and on? I mean will the loop keep repelling the magnet and attracting it over and oer again, or is there a certain time when it stops?
Also theres some things that i didnt really get in your last paragraph. You talked about the magnet going right through the loop, but i thought that as soon as it reaches the begining of the loop, it will be repelled?
Also theres some things that i didnt really get in your last paragraph. You talked about the magnet going right through the loop, but i thought that as soon as it reaches the begining of the loop, it will be repelled?
well the problem is that the loop can never fully repel the magnet, because as the magnet slows down (due to the repulsion), the rate of change of the field slows down, and so the induced field goes down as well. I think the best you can hope for is the magnet comes to a complete stop, but i think that's for the realm of superconductors.
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