Hi

I'm trying to build a small electromagnet to use in a generator. Right now, I have a coil of insulated 16 AWG copper wire wrapped around a large iron nail with a diameter of 1.5cm. The length of the magnet is 12.4 cm, and the wire has 133 turns. I'm connecting it to three 9V batteries wired in parallel.

My question is, how can I calculate the magnetic flux density in Teslas? I found the equation B=kμ0NI, but the number I get is too high to make sense. I also need to know how to calculate the resistance of the coil, and then figure out how much current the batteries can provide, possibly using Ohm's Law.

To calculate the magnetic field induction B in Tesla you need to multiply the current  I flowing in the windings by the total number of turns nand with the permeability of vaccum and the core relative (if applicable) - these can be found in physics tables. The resitance is based on the lenght of the windings and the material they are made of. Have a look at:

http://www.coilgun.eclipse.co.uk/coil_resistance_formula.html

There is a formula for an iron core solenoid electromagnet: 

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/solenoid.html#c3

Hi

I'm trying to build a small electromagnet to use in a generator. Right now, I have a coil of insulated 16 AWG copper wire wrapped around a large iron nail with a diameter of 1.5cm. The length of the magnet is 12.4 cm, and the wire has 133 turns. I'm connecting it to three 9V batteries wired in parallel.

My question is, how can I calculate the magnetic flux density in Teslas? I found the equation B=kμ0NI, but the number I get is too high to make sense. I also need to know how to calculate the resistance of the coil, and then figure out how much current the batteries can provide, possibly using Ohm's Law.