The EarthMagnetic PolesNorth and SouthGeographic PolesNorth and SouthEarth is a giant magnet.
InclinometerAn example of an inclinometer showing theEarth’s magnetic inclination
Compass PointsThe direction of compass points in UnitedStates
Types of MagnetsLOADSTONEBARUCOILALNICO
Natural MagnetMaterial is Magnetite or IronOxide (Fe2 03)
MagnetsA very strong magnet can be made witha coil of wire and the flow of an electriccurrent.
AlnicoAn extremely strong Alnico permanentmagnet with keeper
Theory of MagnetismMolecular and Electron Theories
Creating Magnets The pictureshows that ascrewdriver doesnot pick up paperclips.Methods used to create a magnet
Creating MagnetsStroking using a permanent magnet However, afterstroking thescrewdriver with amagnet, the bladeitself becomesmagnetic andattracts the paperclips.
Flux Magnetic lines offorce Strongest at thepoles
Removing MagnetismHeat is one way to removemagnetism.
Laws of MagnetsPoles attract or repel
Like Poles Repel
Laws of magnets shownby flux linesUnlike poles attract Like poles repel
Stray Lines of ForceControlling stray lines usinga keeper
Magnetic Lines of Force Notice how thematerials are affected Soft iron is a materialthat distorts fluxMagnetism will pass through any material
ElectromagnetsA 30-foot diameter electromagnetused in research for a superconductorA large electromagnetused to lift scrap metal
ElectromagnetsThe source of electromagnetism is electricity(current) flowing through a coil of wire.
ElectromagnetsA coil of wire can be made into a magnet by passing anelectric current through it.Without electricity,there is nomagnetic forceElectric current applied to a coilcreates a magnetic field
Electromagnetic Strength Increase the number of coils. Increase the electric current flowingthroughthe coil. Add an iron core in the center of the coil.How can an electromagnet be madestronger?
The left hand rule todetermine North PoleNORTH POLE SOUTH POLE
Making a MagnetAn example of a very strong magnet
The magnet is strongenough to lift this 50pound engine cylinderhead.The coil of wire has beenattached to a 12 volt DCpower source making anextremely strong magnet.Making a Magnet
SaturationSaturation KneeY- AxisIncreasingMagneticForceYX- Axis Increasing ElectricCurrentXSaturation of a magnetic field occurs when an increase ofelectric current flow does not increase the strength of themagnetic field as shown by the graph. The knee of thecurve is the point that saturation occurs.
MAGNETIC COIL LOSSES Copper losses - resistance of coppercoils. Hysteresis - magnetic flux inducing acurrent in the core. Eddy currents - magnetic polarity of theiron core is rapidly changed by an ACcurrent causing friction and heatbetween the molecules
MAGNETIC TERMS Flux - Invisible lines of force. Poles - North and South where force isstrongest. Permeability – The ability of a material toconduct lines of force. Residual Magnetism – The ability of amaterial to hold its magnetism for a longtime.
MAGNETIC TERMS Ferromagnetic Material – A material easy tomagnetize. (i.e., Iron Steel, Cobalt, Perm-alloy,and Alnico) Paramagnetic Material- A material that can beslightly magnetized. Diamagnetic Material – A material that is verydifficult to magnetize. Magnetic Laws – Simply stated: Like polesrepel and unlike poles attract.
Review What are the poles of a magnet? Name the magnetic lines of force. List five types of magnets and their twofamilies. List the laws of magnets. Explain two methods for making a magnet.
Review Explain two theories of magnetism. Name five different types of devices that areassociated with electromagnetism? List three magnetic and three nonmagneticmaterials. What will remove magnetic lines of force?