Chapter 21

 Electromagnetic induction is the process of generating a current by moving an electrical conductor relative to a magnetic field.  This was discovered by Michael Faraday in  According to Faraday’s law, a voltage is induced in a conductor by a changing magnetic field.

Generators  A generator is a device that converts mechanical energy into electrical energy by rotating a coil of wire in a magnetic field.  These generators are used by power plants to produce electricity for homes.

Transformers  A transformer is a device that increases or decreases the voltage and current in a circuit.  No power is lost in this conversion.  The first coil is the primary coil and the second coil is the secondary coil.  There are two types of transformers.

 A step up transformer converts voltage and current in relation to the ratio of the turns (loops) in the primary and secondary coils.  The voltage goes up and the current goes down in this transformer.

 A step down transformer will do the same thing as the step up but this one will reduce the voltage and increase the current.  These two transformers are used to transport electricity large distances and to convert it for safe use in the house.

Ticket out the door  What is electromagnetic induction?  What is a generator?  How does a transformer work?

 The connection between electricity and magnetism was made in 1820 by Hans Christian Oersted.  Electricity and magnetism are two aspects of a single force known as electromagnetic force.  Both aspects are caused by electric charges.

 Moving electric charges create a magnetic field.  The magnetic field lines form circles around a straight wire carrying a current.

Electromagnets  A coil of current-carrying wire that produces a magnetic field is called a solenoid.  If an iron rod is placed inside the coil, the strength of the magnetic field increases.  An electromagnet is a solenoid with a ferromagnetic core.

 Changing the current in an electromagnet controls the strength and direction of its magnetic field.  The strength can also be affected by the number of loops and the type of core.