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 n Can increase the strength by; –Adding more windings –Increasing the current »More voltage »less resistance –Wrap windings around something with low reluctance

Conventional Theory 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. Says: Current flows From Positive “+” to Negative “-”

Electron Theory 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. Says: Current flows From Negative “-” To Positive “+”

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

Saturation Turn on point Saturation point Turn on point Saturation point Two coil ramps Taken with a Lab Scope and An amp probe. Shorted coil About 4.25 mS

Electromagnet questions?

Relays

Relays n 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 2 & 4 the controlled circuit Send current Thru 1 & 3 to Create field 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 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 Relay

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

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

ISO Mini Relay

ISO Micro Relay

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

Typical horn circuit In steering wheel

Relay Questions? Relay Questions?

Parallel circuit review

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

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

Parallel circuit questions? Lets apply what we Have learned.

Don’t panic! n Apply what you have learned about relays and parallel circuits n 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 n Make sure there is a complete path in the control circuit and the controlled circuit

YOU CAN DO IT! n Apply what you have learned about relays and parallel circuits n 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 n Make sure there is a complete path in the control circuit and the controlled circuit