# Magnetic field solenoid - -

1. Aug 8, 2010

### pat666

1. The problem statement, all variables and given/known data

You have 12m of 0.50mm diameter copper wire and a power supply capable of passing 17A through the wire.
What magnetic field strength would you obtain inside a 2.0-mm-diameter solenoid with the wire spaced as closely as possible?

2. Relevant equations

3. The attempt at a solution
My problem is that I cant find n - tried about 50 times but its always wrong.
n=12/(pi*0.0205) wrong
n=12/(pi*0.02) wrong
n=0.02pi wrong never thought this was right but I cant think of anything else to do??? for a mastering physics online question so no answer yet.

2. Aug 8, 2010

### vela

Staff Emeritus
3. Aug 8, 2010

### pat666

I thought the only limitations were the length of the wire and the radius/diametre of the solenoid???
yeah n is turns/length

4. Aug 8, 2010

### vela

Staff Emeritus
The turns per unit length tells you how closely you can pack the loops next to each other. The overall length of the wire and the size of the solenoid really have nothing to do with that.

5. Aug 8, 2010

### pat666

really, so how do I find out n then???

6. Aug 8, 2010

### pat666

hey, so n will be .0005/something

7. Aug 8, 2010

### vela

Staff Emeritus
Almost! You have 0.0005 m per turn, so you have 1 turn per 0.0005 m, which is 2000 turns/m.

8. Aug 8, 2010

### pat666

Thanks vela!!!!! that problem had me screwed.