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Magnetism

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.

aphrodite-harrington
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Magnetism

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  1. Magnetism Auto 2 after series circuits

  2. Magnets & Magnetic Fields

  3. Magnetic flux lines Flux Always flows from North to South

  4. Opposites Attract / Likes repel

  5. Arrangement of atoms In metal that has not been magnetized

  6. Arrangement of atoms In metal that has been magnetized

  7. Permeability Ability of materials to become magnetized

  8. Reluctance Resistance to magnetic lines of flux High reluctance = Air Low reluctance = Soft Iron

  9. Electromagnetism Any time current flows thru a conductor, A magnetic field is created around the conductor

  10. Electromagnets • Can increase the strength by; • Adding more windings • Increasing the current • More voltage • less resistance • Wrap windings around something with low reluctance

  11. 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.

  12. 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.

  13. Saturation Is the point where the magnetic strength eventually levels off More windings, the longer it takes but the stronger the field

  14. Saturation Shorted coil Two coil ramps Taken with a Lab Scope and An amp probe. Saturation point Turn on point About 4.25 mS Amps = magnetic field Saturation point Turn on point Time in miliseconds

  15. Electromagnet questions?

  16. Relays

  17. 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

  18. Relay in operation 1 & 3 the control circuit Send current Thru 1 & 3 to Create field High current Switched to Load out #2 2 & 4 the controlled circuit Voltage present at #4 Trying to push current Out #2 to high current load

  19. Normally Open (N O) Relay • Takes energy to switch closed • No energy, switch is open • Normally Closed (N C) Relay • Takes energy to switch open • No energy, switch is closed Normally Open and Normally Closed

  20. Normally Open Relay

  21. ISO Mini Relay Most manufactures went to this standard NC NO Terminals #30 to #87a are NC and terminals #30 to #87 NO

  22. Terminals #85 & #86 are the control Circuit (winding) usually 70 ohms ISO Mini Relay Terminal #87 goes to load Controlled circuit Terminal #30 comes from B+ Terminal #87a is rarely used (wiper park circuit)

  23. ISO Mini Relay

  24. ISO Micro Relay

  25. Find control and controlled Circuits with ohmmeter Power up control circuit While checking controlled Checking Relays

  26. Typical horn circuit In steering wheel

  27. Relay Questions?

  28. Parallel circuit review

  29. Parallel Circuit Rules • More than one path • Has a splice in the circuit • Voltage stays the same • Total Amperage is divided between the paths • Total Resistance is always lower that the smallest path or branch

  30. OHMS LAW STILL WORKS THE SAME If volts and ohms Are equal, then One amp will flow.

  31. Parallel circuit questions? Lets apply what we Have learned.

  32. Don’t panic! • Apply what you have learned about relays and parallel circuits • Draw up a typical horn circuit • Remember the horn switch is in the steering wheel • We don’t want to send the high current through the horn switch, so we will use a relay • The horn is the load that will use high amps • Make sure there is a complete path in the controlcircuit and the controlled circuit

  33. YOU CAN DO IT! • Apply what you have learned about relays and parallel circuits • Draw up a typical horn circuit • Remember the horn switch is in the steering wheel • We don’t want to send the high current through the horn switch, so we will use a relay • The horn is the load that will use high amps • Make sure there is a complete path in the controlcircuit and the controlled circuit

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