Magnetism and Electromagnetism Notes (Text p. 582-589)

• The magnetic force is a force that acts at a distance. A magnetic field is the distribution of a magnetic force in the region of a magnet.
• There are 2 different magnetic characteristics, north and south, responsible for magnetic forces. Similar poles repel one another, dissimilar poles attract one another.
• To map a magnetic field, we use a test compass or spread iron filings near a magnet.
• Ferromagnetic metals are metals such as iron, nickel, cobalt, or mixtures of these three that attract magnets. All magnets are made up of these metals.
• Domain Theory of Magnets - All large magnets are made up of many smaller and rotatable magnets, called dipoles, which can interact with other dipoles close by. If dipoles line up, then a small magnetic domain is produced.
• Oersted's Principle - Charge moving through a conductor produces a circular magnetic field around the conductor.
• Right-hand rules used to map the magnetic field and predict the direction of the electromagnetic force created by the current running through conductor.
• Right-hand rule #1 (RHR#1) for conventional current flow (for conductors) - Grasp the conductor with the thumb of the right hand pointing in the direction of the conventional, or positive (+), current flow. The curved fingers point in the direction of the magnetic field around the conductor.
• In order to make the conductor magnet stronger and straighten our its field, the conductor is coiled into a solenoid. The magnetic field around a solenoid is like that of a bar magnet. When wire is coiled, individual field lines fall on top of each other, strengthening the overall field. Linear cylinder shape also straightens out the field.
• Right-hand rule #2 (RHR#2) for conventional current flow (for coils) - Grasp the coiled conductor with the right hand such that curved fingers point in the direction of conventional, or positive (+), current flow. The thumb points in the direction of the magnetic field within the coil. Outside the coil, the thumb represents the north (N) end of the electromagnet produced by the coil.
• Electromagnet - a coil of wire around a soft iron core, which uses electric current to produce a magnetic field.
• Strength of magnetic field represented by B.
• Factors that determine strength of electromagnet: current in the coil, number of turns in coil, type of material in the coil's centre, size of coil.
• Some of the uses of electromagnetism: lifting, relay, electric bell.