MAGNETISM

MAGNETIC FORCES Magnetic force = force a magnet exerts on another magnet, force weakens with square of distance (twice as far, ¼ as much) Magnetic poles = location where force is strongest (At the ends of the magnet)  Two poles: north and south  Like poles repel, opposites attract  Cannot have a single pole (monopole )  What happens when a magnet is split in half? See left. N S

CAN BE DETECTED BY IRON FILINGS OR A COMPASS

Very strong magnetic field between opposite poles, leads to attraction Weak magnetic field between like poles, leads to repulsion

MAGNETIC FIELD AROUND THE EARTH Earth behaves like a giant bar magnet. The magnetic poles are opposite of the geographic poles (see left). Earth’s magnetic field is generated by electric currents in the liquid outer core. Magnetosphere = area around Earth that is influenced by the magnetic field (extends tens of thousands of km into space)

WHAT MAKES A MATERIAL MAGNETIC? Electrons move around the nucleus of an atom (moving charge)  This spinning of electrons causes the electrons to act like little magnets.  In most materials; electrons are paired off and the spin will cancel each other out.  In others (Iron, Nickel and Cobalt) electrons can be unpaired and the spinning of an unpaired electron is what causes a little magnetic field!

ELECTROMAGNETISM In 1820, Hans Christian Oersted “stumbled” across the relationship between electricity and magnetism Electricity and Magnetism- Are part of a single force called the electromagnetic force.  Electric force results from charged particles Magnetic force results from movement of charges

MAGNETIC FIELDS AND MOVING CHARGES Moving charges (Electricity) create a magnetic field as shown Solenoid = coil of current-carrying wire that produces a magnetic field  Ferromagnetic Material = a material that can be magnetized (Iron, Nickel and Cobalt).

ELECTROMAGNETS Electromagnet = solenoid with a ferromagnetic core Magnetic field produced by current causes the ferromagnetic material to become a magnet Strength depends on the current, number of loops, and type of core

MOTORS Uses an electrical current to produce Mechanical motion due to attraction and repulsion of the electromagnet between two permanent magnets.

GENERATOR Device that uses the movement of a magnet near a wire to induce an electrical current. Converts Mechanical Energy into Electrical Energy