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.
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
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)
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)
• E = Voltage
• I = Current
• R = Resistance
Voltage (E) = Current (I) X Resistance
Current (I) = Voltage divided by Resistance
Resistance = Voltage divided by Current (I)
• Test Light
• DVOM (Digital Voltage, Ohmmeter, Ammeter)
• When the electrical path is broken.
• Stops current flow and prevents operation of device.
• Copper to Iron
• Damage to insulated wires.
• Short to Ground
• Short Circuit causes excess current flow.
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.
• Is a solid state electronic device that,
allows the passage of an electrical
current in one direction.
• Current flows from +ve to -ve
• Current flows from +ve to -ve
• Voltage is also known as
• Each circuit should have a
• Power source (Battery)
• Circuit protection device (Fuse)
• Switch (open/close)
• Load (bulb, horn, etc.)
• Conductor (wires)
• 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.
• 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.
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)
Fuses (Protect the circuit from shorts)
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
• 18 gauge is thinner then 12 gauge.
Crimp connectors and terminals
• Quick repair of automotive wiring.
Crimping pliers are used for connectors.
Computer control wires must be soldered for good connection,
and heat shrunk.
Jumper Wire is used to by-pass circuits.
If the component works after by-passing, the component is faulty.
• Google search engine (Images)