2Objectives Observe the magnetic fields of different magnets Recognize magnetism as a force that acts between magnets and magnetic objectsUnderstand how electromagnets are made and how they work
3Main IdeaMagnetism comes from a special alignment of an atom’s electrons as found in iron and many other metals. Electric currents also create magnetic fields.
4Prehistoric PeoplesMagnetism discovered when prehistoric peoples found magnetic rocks called LODESTONESLodestones are mostly iron, and attract or repel certain metals
5TodayScientists know that magnetism is a force created by the motion of electrons in atoms.Moving electrons produce magnetic fieldsElectrons aligned in the same direction, fields around them combine to create a strong magnet
6NonmagneticAtoms of paper and other nonmagnetic materials also have tiny magnetic fields.However, they all point in different directions canceling each other out and do not create a strong magnetic field.See page F30 for picture
7Magnets Atoms are aligned in the same directions This forms two regions called polesNamed North and South
8Poles All magnets have two poles, even if broke in half Bring the like poles together repel each otherBring the opposite poles together attractEach pole is also attracted to earth’s poles
9Making magnetsBring a permanent magnet close to a magnetic material will temporarily change the alignment of its atoms.Example: Rub a magnet along an iron nail and the iron nail will become a magnet temporarily.
10Another way You can also use an electric current Electrons moving through a wire create a magnetic field around the wirePlacing magnetic materials in this field will realign their atoms.This is called ELECTROMAGNETSee page F32 (do class demonstration)
11AurorasAuroras Borealis – also called the northern lights, is seen at night in the northLooks like ribbons of green or redWhy? The earth is a giant magnetFast electrons collide with atoms and molecules of oxygen and nitrogen that make up Earth’s atmosphereThey are attracted by the poles
12Auroras Cont.Auroras are produced in Earth’s polar regions because this is where the magnetic field is strongest.Color depends on gas hit by electrons.Electrons come from the sun.