# making a solenoid from 1.0m of wire. missing information?

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

You have a 1.0 m long copper wire. You want to make an N turn current loop that generates a 1.0 mT magnetic field at the centre when the current is 1.0 A. You must use the entire wire. What will be the diameter of your coil (in centimetres)?

**2. Relevant equations**

B = u0 * n * I

n = N/L

**3. The attempt at a solution**

I put in the variables and solved for n. I got 795.77. Then I know n = number of turns per unit length (N/L) but it seems that some information is missing from the question. I tried setting the unit length to 1.0m (just a random number) which gives 795.77 turns per meter. Then I know each turn uses Pi * diameter of wire. So 795.77(Pi)d = 1.0m solving for diameter i got 4.00×10^-4m or 0.04cm. But this is the wrong answer. It seems as though i would need to be given the total length of the solenoid in order to determine the required diameter.

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

**2. Relevant equations**

**3. The attempt at a solution**

http://ift.tt/P4hCcE

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