# Magnetism Auto 2 after series circuits Magnets & Magnetic Fields

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• MagnetismAuto 2 after series circuits

• Magnets & Magnetic Fields

• Magnetic flux linesFlux Always flows from North to South

• Opposites Attract / Likes repel

• Arrangement of atoms In metal that has not been magnetized

• Arrangement of atomsIn metal that has been magnetized

• PermeabilityAbility of materials to become magnetized

• ReluctanceResistance to magnetic lines of fluxHigh reluctance = AirLow reluctance = Soft Iron

• ElectromagnetismAny time current flows thru a conductor,A magnetic field is created around the conductor

• ElectromagnetsCan increase the strength by;Adding more windingsIncreasing the currentMore voltageless resistanceWrap windings around something with low reluctance

• Conventional TheoryLeft hand thumb rule applies:With left thumb pointing the way currentFlows, your fingers show you whichWay the magnetic field is built around.Says:Current flowsFrom Positive + to Negative -

• Electron TheoryRight hand thumb rule applies:With right thumb pointing the way currentFlows, your fingers show you whichWay the magnetic field is built around.Says:Current flowsFrom Negative -To Positive +

• SaturationIs the point where the magnetic strength eventually levels off

More windings, the longer it takes but the stronger the field

• SaturationTurn on pointSaturation pointTurn on pointSaturation pointTwo coil ramps Taken with a Lab Scope and An amp probe.Shorted coilAbout 4.25 mS

• Electromagnet questions?

• Relays

• RelaysUse a small amount of current to control (switch) a large amount of currentControl circuit has a winding to create a magnetic field (#1 & #3)Low amp circuitAlso called the primaryControlled circuit has a switch to control current flow to a higher amp load (#2 & #4)Also called the secondaryHigh amp circuit

• Relay in operation1 & 3 the control circuit2 & 4 the controlled circuitSend currentThru 1 & 3 toCreate fieldVoltage present at #4Trying to push currentOut #2 to high current loadHigh currentSwitched to Load out #2

• Normally Open and Normally Closed

• Normally Open Relay

• ISO Mini RelayMost manufactures went to this standardTerminals #30 to #87a are NC and terminals #30 to #87 NONCNO

• ISO Mini RelayTerminal #30 comes from B+Terminal #87 goes to loadTerminal #87a is rarely used (wiper park circuit)Terminals #85 & #86 are the controlCircuit (winding) usually 70 ohms

• ISO Mini Relay

• ISO Micro Relay

• Checking Relays

• Typical horn circuitIn steering wheel

• Relay Questions?

• Parallel circuit review

• Parallel Circuit RulesMore than one pathHas a splice in the circuitVoltage stays the sameTotal Amperage is divided between the pathsTotal Resistance is always lower that the smallest path or branch

• OHMS LAW STILL WORKS THE SAMEIf volts and ohmsAre equal, thenOne amp will flow.

• Parallel circuit questions?Lets apply what weHave learned.

• Dont panic!Apply what you have learned about relays and parallel circuitsDraw up a typical horn circuitRemember the horn switch is in the steering wheelWe dont want to send the high current through the horn switch, so we will use a relayThe horn is the load that will use high ampsMake sure there is a complete path in the control circuit and the controlled circuit

• YOU CAN DO IT!Apply what you have learned about relays and parallel circuitsDraw up a typical horn circuitRemember the horn switch is in the steering wheelWe dont want to send the high current through the horn switch, so we will use a relayThe horn is the load that will use high ampsMake sure there is a complete path in the control circuit and the controlled circuit

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