Transcript Magnetism
MAGNETISM AND ELECTROMAGNETISM • 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! • 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. • 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 • All magnets have a north pole and a south pole • Like poles repel. Unlike poles attract • A compass needle is a small bar magnet that can freely rotate • A compass needle always points north, or rather is north-seeking 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 ). MAGNETIC DOMAINS • Microscopic groups of atoms with aligned magnetic poles MAGNETIC MATERIALS • Materials in which the domains will line up in order to form a magnetic field • Examples: iron, cobalt, and nickel WHAT HAPPENS WHEN YOU CUT A MAGNET IN HALF? 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. • The domains of temporary magnets are only aligned when the material is influenced by a magnetic field. (ex. Refrigerator, white board) • 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 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 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!)