Notes: 16.2 The source of Magnetism

Electricity & Magnetism -Current flowing through a wire generates a magnetic field around that wire Electromagnet- magnet created by current flowing through wires

Magnetic field direction- determined by the “right hand rule” for both a single wire and a coil of wires Single wire- thumb points in direction of current, fingers point in direction of mag. field

Coil – fingers point in direction of current flow, thumb points in the North direction

Electromagnet advantages- can switch on/off, can switch directions of poles, can alter field strength with more/less current so they can be VERY strong Uses: doorbell, toaster, electric motors

Factors effecting an electromagnet- *Amount of current *Core material *Number of turns Magnet shape, size and winding pattern also effect the field*

The Walker magnet, weighs 88tons, listed by Guinness as the largest of its kind, has enormous power -- about 270 tons of lifting capacity. It removes iron from Copper ore in mining operations.

All magnetism comes from electric currents Diamagnetic- individual electrons in each atom cancel each other out, so no magnetic field in these materials (lead & diamond) Paramagnetic- each atom has a magnetic field, but the atoms line up to cancel each other out, so not magnetic field (aluminum is an example, but it does have a very weak magnetic field)

Ferromagnetic- material with strong magnetic properties Aligned magnetic domain- each atom’s electrons align with other atoms electrons to increase the total magnetic field strength

Soft magnet –easy to magnetize, but looses its magnetic field easily (steel) Hard Magnet- domains of hard magnets stay aligned for a long time (nickel, cobalt, neodymium) Heat, shock and other magnets can demagnetize a magnet field Liquids and gasses are not permanent magnets as electrons do not stay aligned