Read through and review the course objectives, timetable and evaluation before reading the materials. When they are clear, it's easier to go through the course and understand what you are learning for what you are learning. It is also clear what the assessment needs to be.

After completion of the lesson the student should have acquired following learning outcomes:

1. Describe electricity as it is used in automobiles.

2. Explain the units of electrical measurement, and discuss the relationship among volts, amperes, and ohms.

A typical electrical system

Apart from the main charging, starting and ignition circuits, there are other circuits that power lights, electric motors, the sensors and gauges of electrical instruments, heating elements, magnetically operated locks, the radio and so on.

All Circuits are opened and closed either by switches or by relays - remote switches operated by electromagnets.

Current flows along a single cable from the battery to the component being powered, and back to the battery through the car's metal body. The body is connected to the earth terminal of the battery by a thick cable.

This type of circuit is called an earth-return system any part of it connected to the car body is said to be earthed.

The strength of the current is measured in amperes (amps); the pressure that drives it round the circuit is called voltage (volts). Modern cars have a 12 volt battery. Its capacity is measured in amp/hours. A 56 amp/hour battery should be able to deliver a current of 1 amp for 56 hours, or 2 amps for 28 hours.

If the battery voltage drops, less current flows, and eventually there is not enough to make the components work.

Current, voltage and resistance

The extent to which a wire resists the flow of current is called resistance, and is measured in ohms.

Thin wires conduct less easily than thick ones, because there is less room for the electrons to travel through.

The energy needed to push current through a resistance is transformed into heat. This can be useful, for example in the very thin filament of a light bulb, which glows white hot.

However, a component with a high current consumption must not be connected using wires which are too thin, or the wires will overheat, blow a fuse, or burn out.

All the electrical units of measurement are interrelated: a pressure of 1 volt causes a current of 1 amp to flow through a resistance of 1 ohm. Volts divided by ohms equal amps. For example, a light bulb with a resistance of 3 ohms, in a 12 volt system, consumes 4 amps.

This means it must be connected using wires thick enough to carry 4 amps comfortably.

Often the power consumption of a component will be stated in watts, which are found by multiplying amps and volts. The lamp in the example consumes 48 watts.

Presentation: Electrical fundamentals

Parts of the circuit

All complete circuits must have a power source, a power path, protection (fuse), an electrical load (light bulb in this case), and a return path back to the power source. Return path back to the battery can be any electrical conductor, such as a copper wire or the metal frame or body of the vehicle. Electrical switch opens the circuit and no current flows. The switch could also be on the return (ground) path wire. Short circuit permits electrical current to bypass some or all of resistance in circuit. A fuse or circuit breaker opens the circuit to prevent possible overheating damage in the event of a short circuit.

Short circuits and fuses

If the wrong-sized wire is used, or if a wire becomes broken or disconnected, this can cause an accidental short circuit which bypasses the resistance of the component. The current in the wire may become dangerously high and melt the wire or cause a fire.

The fuse box is often located in a cluster of components, as illustrated here. The box is shown with the cover off.

To guard against this, ancillary circuits have fuses.

The most common type of fuse is a short length of thin wire enclosed in a heatproof casing often glass.

The size of the fuse wire is the thinnest that can carry the normal current of the circuit without overheating, and it is rated in amps.

The sudden surge of high current in a short circuit makes the fuse wire melt, or 'blow', breaking the circuit.

When this happens, see if there is a short circuit or a disconnection, then install a new fuse of the correct amperage rating.

There are many fuses, each protecting a small group of components, so that one blown fuse does not shut down the whole system. Many of the fuses are grouped together in a fuse box, but there may also be line fuses in the wiring.

After completion of the course the student should have acquired following learning outcomes:

1. Diagnose electrical/electronic integrity for series, parallel, and series-parallel circuits using Ohm’s law.

2. Explain Kirchhoff’s voltage law.

3. Calculate voltage drops in a series circuit.

As current flows through a circuit, voltage drops in proportion to amount of resistance in circuit. Most, if not all, of resistance should occur across load such as bulb in this circuit. All of other components and wiring should produce little, if any, voltage drop. If a wire or connection did cause a voltage drop, less voltage would be available to light bulb & bulb would be dimmer than normal. In a series circuit voltage is dropped or lowered by each resistance in the circuit. Higher resistance, greater drop in voltage.

After completion of the course the student should have acquired following learning outcomes:

1. State Kirchhoff’s current law.

2. Explain parallel circuit laws.

3. Calculate voltage drops in a parallel circuit.

After completion of the course the student should have acquired following learning outcomes:

1. Identify a series-parallel circuit.

2. Identify where faults in a series-parallel circuit can be detected.

3. Calculate current flow and voltage drops in a series-parallel circuit.

Series and parallel circuits

A circuit usually includes more than one component, such as bulbs in the lighting circuits. It matters whether they are connected in series one after the other or in parallel side by side.

A headlamp bulb, for example, is designed to have a degree of resistance so that it consumes a certain current to glow normally.

But there are at least two headlamps in the circuit. If they were connected in series, electric current would have to go through one headlamp to get to the other.

The current would encounter the resistance twice, and the double resistance would halve the current, so that the bulbs would glow only feebly.

Connecting the bulbs in parallel means that electricity goes through each bulb only once.

Some components must be connected in series. For example, the sender in the fuel tankvaries its resistance according to the amount of fuel in the tank, and 'sends' a small electrical current to the fuel gauge.

The two components are connected in series so that the varying resistance in the sender will affect the position of the needle on the gauge.

Ancillary circuits

The starter motor has its own heavy cable, direct from the battery. The ignition circuit furnishes the high-tension impulses to the sparkplugs; and the charging system includes the generator, which recharges the battery. All the other circuits are called ancillary (subsidiary) circuits.

Most are wired through the ignition switch, so that they work only when the ignition is switched on.

This prevents you accidentally leaving something switched on which might cause the battery to go flat.

The side and tail lights, however, which you may need to leave on when the car is parked, are always wired independently of the ignition switch.

When fitting extra accessories, such as a rear window heater which consumes a heavy current, always wire it through the ignition switch.

Some ancillary components can be operated without the ignition turned on by turning the switch to the 'auxiliary' position. A radio is usually wired through this switch, so that it can be played with the engine off.

After completion of the course the student should have acquired following learning outcomes:

1. Explain the wire gauge numbering system.

2. Describe how fusible links and fuses protect circuits and wiring.

3. List the steps for performing a proper wire repair.

4. Perform solder repair of electrical wiring.

5. Discuss circuit breakers and PTC electronic circuit protection devices.

6. Explain the types of electrical conduit

Presentation: Automotive wiring and wire repair

After completion of the course the student should have acquired following learning outcomes:

1. Interpret wiring schematics.

2. Locate shorts, grounds, opens, and resistance problems in electrical circuits, and determine necessary action.

3. Inspect and test switches, connectors, relays, solid state devices, and wires of electrical circuits, and perform

necessary action.

Presentation: Wiring Schematics and Circuit Testing

After completion of the lessons the student should have acquired following learning outcomes:

1. Explain how magnetism and voltage are related.

2. Explain how an electromagnet works.

3. Describe how an ignition coil works.

Presentation: Magnetism&Electromagnetism

After completion of the lessons the student should have acquired following learning outcomes:

1. Identify semiconductor components.

2. Discuss where various electronic and semiconductor devices are used in vehicles.

3. Explain necessary precautions when working with semiconductor circuits.

4. Describe how diodes and transistors work, and how to test them.

5. Identify the causes of failure of electronic components.

Presentation: Electronics Fundamentals

After completion of the course the student should have acquired following learning outcomes:

1. Describe how a battery works.

2. Describe deep cycling.

3. Discuss how charge indicators work.

4. List battery ratings.

5. Identify the causes of failure of electronic components.

Positive and negative polarity

Electricity flows from a battery in one direction only, and some components work only if the flow through them is in the correct direction.

This acceptance of a one-way flow is called polarity. On most cars the negative () battery terminal is earthed and the positive (+) one feeds the electrical system.

This is called a negative earth system, and when buying an electrical accessory a radio, for example check that it is of a type suitable for your car's system. Fitting a radio with the incorrect polarity will damage the set, but most car radios have an external switchfor setting the polarity to suit that of the car. Switch to the correct setting before fitting.

Presentation about Batteries

Presentation about Battery testing and service

After completion of the course the student should have acquired following learning outcomes:

1. Discuss how to safely set up and use a fused jumper wire, a test light, and a logic probe.

2. Explain how to safely and properly use a digital meter to read voltage, resistance, and current, and compare to factory

specifications.

Presentation: Circuit Testers & Digital Meters

After completion of the course the student should have acquired following learning outcomes:

1. Compare the different types of oscilloscopes and explain how to setup and adjust oscilloscopes.

2. Discuss DC and AC coupling, pulse trains, channels and triggers.

3. Explain how to use a scope and discuss graphing multimeters and graphing scan tools.

Presentation: Oscilloscopes &Graphing Multimeters