## ELECTRICITY GENERATION Remember Ohms law from last time. Here are two circuits below. If you know Ohms law you should be able to make the light come on in one only one try as the amperage, I, is now specified. In the early 19th century the following similarity between two charged particles and two magnets was observed: both created "forces" that could operate in a vacuum charge had a postive and negative component; magnets had a north and south pole force could then be either attractive or repulsive. both the magnetic force and the electrostatic force strength decreased as 1/R2 In 1820 Oersted did this experiment: and discovered that an electric current creates a magnetic field Similarly, a coil of wire with a current passing through it generates a magnetic field. This is known as an electromagnet or solenoid . So now we know that a current can create a magnetic field. If a magnetic field can create a current then we have a means of generating electricity. Experiments showed that a magnetic just sitting next to a wire produced no current flow through that wire. However, if the magnet is moving a current is induced in the wire. The faster the magnet moves, the greater the induced current. This is the principal behind simple electric generators in which a wire loop is rotated between to stationary magnetics. This produces a continuously varying voltage which in turn produces an alternating current . These ideas were first suggested by Michael Faraday and Farady's law states that the voltage is proportional to the rate of change of the magnetic flux. In the diagrams below, this magnetic flux is represented by blue vectors going from North to South. Diagram of a simple electric generator: 