# Homework Help: Iron piece movement

1. Jun 15, 2011

### epilot

Hello guys,

I want to know if I apply a DC voltage to the wire winding then what will happen to the iron piece and why? What if the voltage happens to be AC??
I think that the iron piece will move but how and why, I am not sure...

Thanks for any help

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2. Jun 15, 2011

### Staff: Mentor

For background and some equations, check out the Electromagnetic Solenoid portion of this wikipedia page:

http://en.wikipedia.org/wiki/Solenoid

.

3. Jun 16, 2011

### epilot

Thanks, But I couldn't get my response!

4. Jun 16, 2011

### Staff: Mentor

What does that mean? Do you have questions about the wikipedia article?

5. Jun 16, 2011

### RTW69

This would be a great experiment and easy to do. Try it!

My guess is that the metal bar doesn't move. Running a DC current in a coil around a horseshoe shaped bar will magnetize it with one end of the horseshoe north the other side south depending on the direction of current flow. Essentially you end up with a horseshoe magnet. If you place a metal bar on one end of a horseshoe magnet the attractive forces at contact will be greater than the attractive forces between the end of the metal bar and the other end of the horseshoe electromagnet. Remember attraction lessens with distance.

Get a cheap horse shoe magnet, stick a piece of metal on one end and see if it moves. I am guessing not. That is my hypothesis. Great opportunity to experiment.

6. Jun 16, 2011

### epilot

!!!!
Please be noticed that the under surface happens to be iron as well.
I think the response is something related to the flux in the lower surface.

7. Jun 16, 2011

### Staff: Mentor

Neither of you are reading the tutorial wikipedia article, are you...?

8. Jun 17, 2011

### RTW69

Actually I did look through the Wikipedia solenoid article. Based on epilot's picture it appears that we are talking about an electromagnet. I also reviewed the Wikipedia's electromagnet article. We have a magnet field concentrated in the core of a U shaped electromagnet. A metal bar is placed on one pole of the electromagnet as per the diagram supplied. The question is does the metal bar move when a DC current is applied. Is that correct epilot or am I missing something? I am curious as to what Berkeman thinks will happen.