PS-6.11  Explain the relationship of magnetism to the movement of electric charges in electromagnets, simple motors, and generators.
Key Concepts:
Electromagnet:  core, coil
Motor:  armature
Generator:  electromagnetic induction
The operation of almost all electrical devices you use today is based on some very simple concepts. Everyone knows that a simple bar magnet is surrounded by an invisible magnetic field. Simply put, permanent magnets are magnetic because the electrons within the iron atoms of the magnet have their own magnetic field. When the electrons within the iron or steel bar magnet are lined up in the same direction the magnetic field of the electrons combine to make the bar magnetic as illustrated in diagram "A".
Diagram A  
Another way to make a magnet is to pass an electric current along a conductor such as a wire. An electrical current flowing in a conductor produces a magnetic field around the conductor. When an electrical current is moving in a conductor the electron align. This produces a magnetic field around a conductor. The strength of the magnetic field depends on the strength of the current. A high current produces a strong magnetic field while a smaller current produces a weaker magnetic field. Diagram "B" illustrates the magnetic field around a wire conductor when an electric current is flowing on the conductor. A magnetic compass can be used to detect this invisible magnetic field. There is obviously a very close relationship between electricity and magnetism.
If the wire conductor is wrapped into a coil, the magnetic field lines overlap, and the magnetic field is multiplied. If the coil is wrapped around an Iron core, the Iron core concentrates the magnetic field, producing an electromagnet ( See diagram "C"). Electromagnets are one of the primary components in many electrical devices. Electric motors, speakers , and even microphones contain electromagnets. Large electromagnets are used to lift heavy loads of scrap Iron.
Very often in science, if one fact is true, the opposite is also true. We just learned that an electric current moving along a conductor produces a magnetic field around a conductor. In 1861 Michael Faraday discovered that the opposite is also true, pass a magnetic field across a wire conductor and an electric current is created. This happens because the magnetic field pushes or pulls the electrons in the conductor. This process of producing an electric current by moving a wire within a magnetic field is called electromagnetic induction. The moving magnetic field induces an electric current in the conductor.