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Magnetism Auto 2 after series circuits Magnets Magnetic Fields Magnetic flux lines Flux Always flows from North to South Opposites Attract Likes repel Arrangement of atoms In metal that has not been magnetized Arrangement of atoms In metal that has been magnetized Permeability Ability of materials to become magnetized Reluctance Resistance to magnetic lines of flux High reluctance Air Low reluctance Soft Iron Electromagnetism Any time current flows thru a conductor A magnetic field is created around the conductor Electromagnets Can increase the strength by Adding more windings Increasing the current More voltage less resistance Wrap windings around something with low reluctance Conventional Theory Says Current flows From Positive to Negative Left hand thumb rule applies With left thumb pointing the way current Flows your fingers show you which Way the magnetic field is built around Electron Theory Says Current flows From Negative To Positive Right hand thumb rule applies With right thumb pointing the way current Flows your fingers show you which Way the magnetic field is built around Saturation Is the point where the magnetic strength eventually levels off More windings the longer it takes but the stronger the field Saturation Shorted coil Saturation point Turn on point Turn on point About 4 25 mS Saturation point Two coil ramps Taken with a Lab Scope and An amp probe Electromagnet questions Relays Relays Use a small amount of current to control switch a large amount of current Control circuit has a winding to create a magnetic field 1 3 Low amp circuit Also called the primary Controlled circuit has a switch to control current flow to a higher amp load 2 4 Also called the secondary High amp circuit Relay in operation 1 3 the control circuit Send current Thru 1 3 to Create field 2 4 the controlled circuit Voltage present at 4 Trying to push current Out 2 to high current load High current Switched to Load out 2 Normally Open and Normally Closed Normally Open N O Relay



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