How to build an electricmagnet?

Question

Okay, so I've got a two 12 volt batteries, and I want to make an electricmagnet. How do I determine how many loops of the wire needed to create a certain magnetic-field strength? What is the formula? What if I use iron core or nickel-core, how does this affect the strength, specifically in gauss? Please help.

Answer 1

there are many more variables here that you are not mentioning so it is impossible to give an exact Gauss answer. but a few general answers.

more turns = bigger magnetic field. iron/nickel core yes electromagnets do need a core iron/nickel will be strongest.  

Answer 2

This is a good question. I do hope the following information is very helpful.

The magnetic field of an electromagnet (which is a solenoid) is given by B = µNI / L, where B is the magnetic field strength (in Teslas), N is the number of turns, I is the current (in Amperes), and L is the length (in meters).

To determine the current, you need to use Ohm's Law, which is I = V / R. You know that the voltage is 12 V, but you must determine the resistance of the wire. The resistance of a wire is given by R = ρL / A, where R is the resistance (in Ohms), ρ is the resistivity (in Ohms meters), L is the length (in meters), and A is the area (in meters squared).

The resistivity of a copper wire heated at 20°C is 1.7 x 10^-8 Ω·m. Determine the radius, area, and length of the wire and calculate the resistance of the wire.

Once you have calculate the current, determine the number of turns of the electromagnet and the length of it as well. Use the formula I provided earlier to determine the magnetic field strength. The magnetic permeability (µ) is 4π x 10^-7 T·m/A. To convert Teslas into Gausses, simply multiply by 10,000.

Adding an iron core or nickel core changes the magnetic permeability. Air itself does not have a magnetic permeability of 4π x 10^-7 T·m/A, but it shouldn't be much different.