Voltage and Current in an Electromagnet I'm having a little bit of trouble with electromagnets. I know that a magnetic field is induced by current flowing through a conductor, but what role does voltage play? Does it have an effect on the force of said electromagnet?
I am trying to build a somewhat powerful electromagnet for a project. Let's say I wanted 100N of force. Should I increase my I or my V to get that force?
 A: Voltage causes current to flow. You may be familiar with Ohm's Law, where current flowing across a resistor (the electromagnet in this case) is proportional to the voltage across it. Thus, if the voltage across the electromagnet is increased, the current flowing through it will increase too. Thus, you cannot increase 'only' voltage or current; rather, you increase one of them and the other increases automatically.
For your particular situation, if you want to increase the current flowing through it, it depends on the type of power source you have. If it is a current source, simply increase the current. If it is a voltage source, increase the voltage. 
A: Increasing the voltage you let flow the electrons faster. Increasing the current (by a more powerful source) you send more electrons per time unit through the wire. Both lead to more heat in the wire. This heat is energy that is lost for the magnetic field you try to build. 
To prevent the coil from producing too much thermal energy you have to scale the wire diameter (or to use parallel wires). And you could use a steel kernel to canalize the magnetic field and to lower the self induction processes.
Last not least you could lengthen the coil, of course with more windings. This you can't do to infinity because there is a magnetic saturation of the kernel as well as of the whole system.
To draw the full picture, one can cooling the cool to very low temperatures and use special materials for the wire and one get a super strong magnet without any lost of energy in the wire (but with loses in the cooling system).
