MagnetismChapters 36 & 37
General Info.Moving charges cause magnetismMagnets have magnetic fields around them. (Magnetism acts at a distance. ) Magnets always have two, opposite poles (north and south).Like poles repel and unlike poles attract.Compasses are magnetsSpinning electrons are magnets
Can any material be magnetized?Non-magnetic material
Magnetic materialNoonly materials which have aligned unpaired, electrons can be magnetized!
Ferromagnets (Permanent Magnets)Fe, Ni, and Co have unpaired electrons are aligned in areas called domains.Each domain has a magnetic field.When domains are aligned, material has an overall magnetic field.Pieces of Fe, Ni, and Co become magnetized when they are placed in a strong magnetic field which aligns their domains .
ElectromagnetsDEF: magnet with a field produced by electric currentUsually a coil of wire with current and Fe core
How could you make an electromagnet stronger?Add coilsIncrease currentIncrease amount of Fe inside
Force FieldsEvery ________ is surrounded by a gravitational field because it attracts every other _________.Every ________ is surrounded by an electric field because it attracts or repels every other ________.Every _______ is surrounded by a magnetic field because it attracts/repels every other ____________.
Test Your Knowledge
ParticleGrav Field?Elec Field?Mag Field?Stationary neutronMoving neutronStationary protonMoving protonStationary electronMoving electron
Magnetic FieldsDEF: the area around a magnet where a force acts on a moving charge (another magnet, a current-carrying wire, an electron, etc)Represented by field lines which show direction and strength of force; lines point from north to south; closer lines mean stronger field
Bar MagnetEarths magnetic field looks like that of a bar magnet!
Earths FieldThought to be caused by moving charges in Earths outer core (which is liquid).Protects life on Earth from harmful radiation (moving charges from space).Changes strength and direction over time. Sometimes disappears altogether!
What did you learn today?1. List two types of metals that can be magnetized.2. Sketch the magnetic field lines for a bar magnet.3. Sketch the magnetic field lines of Earth.4. In what ways is Earths magnetic field important to life as we know it?
Right hand rule #1Field around a current-carrying wirethumb in direction of current, fingers curl in direction of field
Right hand rule #2Field inside a coil of wirefingers in direction of current, thumb points in direction of field
Right hand rule 3Force on a current-carrying wire/moving charge in a magnetic fieldMake an Lfingers in direction of magnetic field, thumb in direction of current, palm points in direction of force on charge
How would the direction of the force differ on a positive charge? A negative charge?
Right Hand RulesField around a current-carrying wirethumb in direction of current, fingers curl in direction of fieldField inside a coil of wirefingers in direction of current, thumb points in direction of fieldForce on a moving charge in a magnetic fieldMake an Lfingers in direction of magnetic field, thumb in direction of moving charge, palm points in direction of force on charge
Right Hand Rule Applethttp://www.walter-fendt.de/ph14e/