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# Leacture 8 electrical systems

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### Leacture 8 electrical systems

1. 1. Electrical Systems Conductors good electrical conductors. Copper, Steel, Gold and Silver Insulators poor electrical conductors. Plastic, Rubber and Glass • Traditionally current flow form +ve to -ve • Electron flow theory (Ohms Law) electrons flow from –ve to +ve • Magnetic field is developed when current passes through a wire.
2. 2. Electrical Systems Voltage is a measurement of the pressure that causes the electrical energy(Current) to flow. • Same as water through pipe. • No movement unless force or pressure is applied. • Is measure in volts (V) and the symbol is E
3. 3. Electrical Systems Current current flow is created when voltage moves electrons through a conductor. • This flow is measured in amperes and the symbol is A • Must be a complete circuit before the current can flow. DC Direct Current flow (Automotive) AC Alternating Current it changes its direction of flow (House)
4. 4. Electrical Systems Resistance is opposition to current flow. • Amount is measured in Ohms • Symbol R or Ω Resistance of a conductor depends on: • Type of material. • Size or material (Wire Gauge) • Length of the conductor. • Temperature of the conductor (Lower the temperature, less the resistance)
5. 5. Electrical Systems OHMS Law • E = Voltage • I = Current • R = Resistance Voltage (E) = Current (I) X Resistance Current (I) = Voltage divided by Resistance Resistance = Voltage divided by Current (I)
6. 6. Electrical Systems Circuit Testers • Test Light • DVOM (Digital Voltage, Ohmmeter, Ammeter)
7. 7. Electrical Systems Open Circuit • When the electrical path is broken. • Stops current flow and prevents operation of device. Reasons • • • • Burned fuse Light bulbs Broken wires Defective switch
8. 8. Electrical Systems Grounded Circuit • Copper to Iron • Damage to insulated wires. • Short to Ground • Short Circuit causes excess current flow.
9. 9. Electrical Systems Excessive Resistance is the most common problem on vehicles. • Lose or dirty connections. • Undersized wires or cables. • Broken strands of wire. • Excessive heat buildups. • Burned switch contacts. • Excessively long wires.
10. 10. Electrical Systems Diode • Is a solid state electronic device that, allows the passage of an electrical current in one direction. • Current flows from +ve to -ve
11. 11. ELECTRICAL CIRCUTS • Current flows from +ve to -ve • Voltage is also known as electrical pressure. • Each circuit should have a • Power source (Battery) • Circuit protection device (Fuse) • Switch (open/close) • Load (bulb, horn, etc.) • Conductor (wires)
12. 12. ELECTRICAL CIRCUTS SERIES CIRCUIT • Power source and loads are in series. • If the path is broken, no current flows. (Christmas lights) • Voltage is divided between the loads. • Current flow is same throughout the circuit. • The resistance of each load can be different.
13. 13. ELECTRICAL CIRCUTS PARALLEL CIRCUIT • More then one path for current flow. • In the event of an open in one branch, current will continue to flow through the remaining. • Each branch receives source voltage. • Current flow and resistance of each branch could be different.
14. 14. ELECTRICAL CIRCUTS AUTOMOTIVE ELECTRICAL CIRCUITS(One wire circuit) • Negative battery cable is attached to the car frame. • Negative from each load is connected to the car frame. • Vehicle’s body or frame acts as a conductor (wire)
15. 15. Circuit Protection Fuses (Protect the circuit from shorts)
16. 16. Fuses Circuit Protection
17. 17. Wiring Type Primary Wire is small and carries battery or alternator voltage. • Colour coded • Wiring size is measured in GAUGE • The thinner the wire, the higher the gauge number • 18 gauge is thinner then 12 gauge.
18. 18. Wiring Repair Crimp connectors and terminals • Quick repair of automotive wiring. Crimping pliers are used for connectors.
19. 19. Wiring Repair Computer control wires must be soldered for good connection, and heat shrunk.
20. 20. Wiring Jumper Wire is used to by-pass circuits. If the component works after by-passing, the component is faulty.
21. 21. Electrical Systems Credits • Google search engine (Images)