- #1
iceworm
- 16
- 0
Good morning:
I'm looking for information on electromagnets for attracting non-ferrous metals. One of the kids on the block is asking for assistance in research for a science fair project. She has a 1951 pamphlet describing the effect. And I found a construction article, but very little explaining the physics.
I won't do the project, but I will assist with the research. And it would be nice if I understood the physics. I fully expect to get asked for explanations. This subject didn't come up when I was going to school 40 years ago and it hasn't come up in the last 40 years working in the electrical power field.
The building of a coil isn't the the main issue. The science fair part is to propose a hypothesis, and then test. And that means understanding the physics. I don't know enough about it to make any suggestions.
Here is what I think I know so far:
If one lays a copper washer on the face of an AC powered electromagnet, the magnetic field through the copper washer induces a current going around the washer. This circulating current induces a magnetic field looping through the center of the washer, opposite polarity to the electromagnet. This repels the copper washer from the electromagnet. This should be an application of Lentz's Law.
Now if one puts two washers on the face of the electromagnet, both are repelled from the electromagnet. However, the two washers are attracted to each other. Their magnetic fields have the same polarity.
So, if the first washer is mechanically fastened to face of the electromagnetic so it can not move, then the second washer will be attracted to the first.
What I don't understand yet (of many things)
How come the electromagnet doesn't push the second washer away?
Is the attraction between the two washers more than the repulseive effect of the electromagnet on the second washer?
I don't mind doing the reading. So If anyone has any references - that would be gracious.
Oh, if my explanation is goofed up, I'd be interested in knowing that as well.
Thanks
ice
I'm looking for information on electromagnets for attracting non-ferrous metals. One of the kids on the block is asking for assistance in research for a science fair project. She has a 1951 pamphlet describing the effect. And I found a construction article, but very little explaining the physics.
I won't do the project, but I will assist with the research. And it would be nice if I understood the physics. I fully expect to get asked for explanations. This subject didn't come up when I was going to school 40 years ago and it hasn't come up in the last 40 years working in the electrical power field.
The building of a coil isn't the the main issue. The science fair part is to propose a hypothesis, and then test. And that means understanding the physics. I don't know enough about it to make any suggestions.
Here is what I think I know so far:
If one lays a copper washer on the face of an AC powered electromagnet, the magnetic field through the copper washer induces a current going around the washer. This circulating current induces a magnetic field looping through the center of the washer, opposite polarity to the electromagnet. This repels the copper washer from the electromagnet. This should be an application of Lentz's Law.
Now if one puts two washers on the face of the electromagnet, both are repelled from the electromagnet. However, the two washers are attracted to each other. Their magnetic fields have the same polarity.
So, if the first washer is mechanically fastened to face of the electromagnetic so it can not move, then the second washer will be attracted to the first.
What I don't understand yet (of many things)
How come the electromagnet doesn't push the second washer away?
Is the attraction between the two washers more than the repulseive effect of the electromagnet on the second washer?
I don't mind doing the reading. So If anyone has any references - that would be gracious.
Oh, if my explanation is goofed up, I'd be interested in knowing that as well.
Thanks
ice