The motion of the turbines drives the generator into motion. The rotors move and also rotate the gears within: armature, rotor, and shaft and together in motion. The armature is a coil of copper wire and on either side are polar field magnets which create a magnetic field inside the generator. The turbines rotate the armature through the magnetic field and an electrical current is created. The copper coil generates more electricity when it spins faster; this is controlled by the speed of the wind outside the blades. The generators produce electricity at a low voltage and a step-up transformer increases the transmission voltage to send out to the city.