17.1 The magnetic force
1. Magnetic field – the distribution of a magnetic force in the region of a magnet. There are two magnetic characteristics, labeled north and south, that are responsible for magnetic forces. Similar poles repel one another, dissimilar poles attract one another.
2. Earth is like a giant permanent magnet, producing its own magnetic field. It is suggested that earth’s magnetic field is produced because of the flow of hot liquid metals inside earth.
3. Magnet forces don’t act just between two magnets; they also attract certain metals such as iron, nickel and cobalt. These metals are called ferromagnetic metals. All magnets are made up of these metals.
4. Domain theory: 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.
17.2 Electromagnets
5. Oersted’s principle: charge moving through a conductor produces a circular magnetic field around the conductor.
6. Right hand rules are developed to help you predict how magnetic forces act.
7. Right hand rule #1 (for conventional current flow): grasp the conductor with the thumb of the right hand pointing in the direction of conventional current flow. The curved fingers point in the direction of the magnetic field around the conductor.
8. Right hand rule #2 (for conventional current flow): gasp the coiled conductor with the right hand such that curved fingers point in the direction of conventional (positive) current flow. The thumb points in the direction of the magnetic field within the coil. The thumb represents the north of the electromagnet.
9. Factors that determine the strength of an electromagnet:
1. Current in the coil
2. Number of turns in the coil
3. Type of material in the coil’s centre
4. Size of coil
10. Left hand rule works the same way as right hand rule, the only difference is that left hand rule is the rule of the flow of charge(- to +), and the rule uses the left hand to complete.
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