Did you know that a wire does not have to be connected to a battery for a current to flow? Current can be induced in a wire by a magnet! All charged particles have an electric field, and all moving charged particles have a changing electric field and an induced magnetic field. Fields allow charged particles to interact with each other without coming into contact. Back in the nineteenth century, Michael Faraday made some really important discoveries about the relationship between electric fields and magnetic fields. He found that a moving charged particle (also called current) has a changing electric field which in turn induces a magnetic field. For example, a current carrying wire induces a magnetic field which goes around the wire. He also found that a changing magnetic field induces a changing electric field, and this is why current does not need a battery to flow. To demonstrate, take a loop of wire and a magnet. A magnet has a magnetic field, but when it moves, the field becomes a changing magnetic field. When a magnet moves through the inside of the loop, a current (changing electric field) is induced in the wire because the magnet has a changing magnetic field. Unlike a changing electric field inducing a magnetic field, a changing magnetic field induces an external changing electric field. Thus, there needs to be another charged particle near the object with a changing magnetic field for it to induce a changing electric field.
Wind turbines are a special type of generator: a machine that converts mechanical energy into electric energy. Generators use the principle described above in which an external changing electric field can be induced by a changing magnetic field. A wind turbine is composed of five main parts: the rotor, the low speed shaft, the gear box, the high speed shaft, and the generator. The rotor is formed by the three large blades and the hub and is connected to the low speed shaft. The gearbox acts like a middleman between the low speed and high speed shafts. The generator is attached to the high speed shaft. When wind moves the blades, the low speed shaft begins the spin a relatively slow rate of 30-60 rotations per minute. The gear box’s job is to take the spinning from the low speed shaft, make it crazy fast, and then spin the high speed shaft at this new incredibly fast rate which ranges between 1,000 and 1,800 rpm! Inside the generator, the high speed shaft is connected to a large magnet which sits inside a drum of wire coils called a scator. As the high speed shaft spins, the magnet spins and a changing magnetic field is created. This induces a changing electric field which means that current flows in the wire coils!