So what produces a solenoid's magnetic field? Voltage or Power? Voltage = Current * Resistance Power = Current^2 * Resistance Magnetic field magnitude of a solenoid = magnetic constant * turns * current We can quadruple the turns using the four times of the same type of wire, but that will quadruple the resistance. We can then double the voltage, but that will still leave us with half the current. Power here doesn't change. However turns quadrupled and current is half. More magnetic field? Alternatively, with the same voltage, we can double the turns using the same type of wire, but that will double the resistance and give us half the current. Voltage would remain the same, and the ampere-turns would remain the same! The power does not! So why do they say that power is needed to produce a magnetic field? Why isn't it voltage that produces the magnetic field?