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Published byKevin Robbins Modified over 9 years ago
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MAGNETISM AND ELECTROMAGNETISM
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Magnetism = the phenomenon of physical attraction for iron observed in magnets, inseparably associated with moving electricity and characterized by fields of force Magnetic force increases as magnets move closer together!
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A magnetic field surrounds a magnet and is strongest at the poles; it is produced by the motion of electric charge. Both the orbital & spinning motion of every electron in an atom produce magnetic fields.
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Magnetic field lines: arrows drawn from north to south poles representing the magnetic field. Number of field lines indicates the relative strength of the magnet
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All magnets have a north pole and a south pole Like poles repel. Unlike poles attract
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A compass needle is a small bar magnet that can freely rotate A compass needle always points north, or rather is north-seeking
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INTERESTING FACT… The northern lights (aurora borealis) & southern lights (aurora australias) are results from the interaction between the solar wind and earth’s magnetic field (makes the air glow ).
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MAGNETIC DOMAINS Microscopic groups of atoms with aligned magnetic poles
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MAGNETIC MATERIALS Materials in which the domains will line up in order to form a magnetic field Examples: iron, cobalt, and nickel
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WHAT HAPPENS WHEN YOU CUT A MAGNET IN HALF?
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PERMANENT MAGNETS Material that keeps its magnetic properties, even when it is not close to other magnets Made by placing a magnetic material in a strong magnetic field, which causes the domains to remain aligned.
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The domains of temporary magnets are only aligned when the material is influenced by a magnetic field. (ex. Refrigerator, white board)
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Electromagnet – temporary magnet that is created by electric current flowing in a wire, usually in the form of a wire coiled around a piece of iron Magnetic field is present only when current is flowing in the wire coil
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Strength of an electromagnet depends on three factors: amount of current in the wire amount of iron or steel in the core number of turns in the coil
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PRODUCING ELECTRIC CURRENT Electromagnetic induction – the production of an electric current by moving a loop of wire through a magnetic field or moving a magnet through a wire loop (which changes the magnetic field near the conductor; no battery!)
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