Automotive Electrics Course Motor Vehicle Section Automotive Electrics Course Level 1

Morning Contents Day One Contents Atomic Structure Conductors (Copper) Insulators (Plastics/Rubber) Units of Electrical Measure Current (Amps) Voltage (Potential Difference & EMF) Resistance (Ohm’s) Power (Watts) Basic Symbols and Circuits Circuit Symbols Series circuits and calculations Parallel circuits and calculations

ELECTRONICS - The Basics Atomic Structure All matter is composed of substances called ‘ELEMENTS’. Elements are the purest and simplest substances and make up the ‘PERIODIC TABLE’, something that you may have heard mentioned in Chemistry lessons at school. For example the Chemical make up of ‘WATER’ is given as H2O. Two parts (Atoms) of Hydrogen combined with one part (Atom) of Oxygen. A Molecule of Water.

ELECTRONICS - The Basics PERIODIC TABLE

ELECTRONICS - The Basics Atomic Structure electrons nucleus protons neutrons

Positive ION Negative ION

ELECTRONICS - The Basics Atomic Structure Neutrons do not carry an electrical charge, combine with protons, which are positively charged to make up the nuclei of all atoms, neutrons and protons do attract each other strongly when they are close together in the nucleus of an atom. However, electrons, which are negatively charged, are held much more weakly to atoms, and it is this weakness upon which electronics is based.

ELECTRONICS - The Basics Atomic Structure It is thought that Electrons orbit the nucleus of atoms in shells (like the planets orbiting the sun). In these shells there should be a specific number of electrons. The number of electrons in the shells will be dependant on the element/material in question, but the inner shells are always filled before the outer shells. If an atom has a complete outer shell, then it is thought that the electrons are tightly bonded and the material will not conduct electricity very well (INSULATOR)

Please complete Exercise 1 in the assessment book The above gives details of Coppers atomic structure, with a single electron in the outer shell, which can be passed from atom to atom. A GOOD CONDUCTOR. Please complete Exercise 1 in the assessment book

Please complete Exercise 1 in the assessment book The above gives details of Coppers atomic structure, with a single electron in the outer shell, which can be passed from atom to atom. A GOOD CONDUCTOR. Please complete Exercise 1 in the assessment book

When a link is placed across a battery then the surplus electrons in the NEGATIVE end of the battery try to fill the ‘holes’ at the POSITIVE end of the battery The Rate of Flow of Electrons from the negative side of the battery to the positive side of the battery is called CURRENT FLOW

A battery when fully charged is filled with positive ions at one end and negative ions at the other

The difference in pressure causes electrons to flow, this potential difference is called VOLTAGE 50 psi 50 psi 100 psi 0 psi

If a restriction is now put into the link this has the effect of reducing the electron(current) flow This is call a RESISTOR and is measured in OHMS

To help understanding of the basic principles it often helps to use a WATER ANALAGY Water pressure Voltage (volts) Water Flow Current (amps) Tap Resistor (Ohms) Turbine Power (watts)

Lets now analyse this Statement OHMS LAW (Ω) G S Ohms in 1827 Stated that; The current flowing through a metallic conductor at a constant temperature is proportional to the potential difference applied to its ends Lets now analyse this Statement

The current flowing through a metallic conductor The amount of current flow in a circuit, measured in amps Metallic conductor could be a length of copper wire

is proportional When one goes up the other goes up, and when one goes down the other goes down

potential difference applied to its ends The difference in electrical potential at either end - Voltage Measured in volt

The current flowing through a metallic conductor at a constant temperature is proportional to the potential difference applied to its ends If there is an increase in voltage then there will be a corresponding increase in current flowing If there is an increase in resistance then there will be a corresponding decrease in current flowing

VOLTS = AMPS X RESISTANCE therefore VOLTS = AMPS X RESISTANCE OR AMPS = VOLTS RESISTANCE RESISTANCE = VOLTS AMPS

V = Voltage (Volts) I = Current (Amps) R = Resistance (Ohm’s) V R I

Please complete Exercise 2 in the Assessment book Ohm’s Law Example In a 24volt truck circuit, what would be the current flow through a 3Ω resistor? 8 A ‘s Please complete Exercise 2 in the Assessment book

CIRCUITS

A circuit consists of A Supply such as a Battery, A Component such as a Bulb, A method of control such as a switch And Sufficient wiring to allow current to flow from one side of the battery to the other A CIRCUIT PROTECTION DEVICE A FUSE

Circuit Symbols To ensure repair personnel can attend to failures in electrical circuits. Components are given designated symbols for universal standardisation. The most common standards these days are IEC (International Electrotechnical Commission) or DIN (Deutsches Institut für Normung ). Which are replacing the old British Standard. Examples of some of these symbols will be discussed on the next few slides.

THE CURRENT HAS TO FLOW THROUGH EACH RESISTOR IN TURN TYPES OF CIRCUIT SERIES CIRCUIT THE CURRENT HAS TO FLOW THROUGH EACH RESISTOR IN TURN

THE CURRENT SPLITS AND DIVIDES BETWEEN EACH BRANCH IN THE CIRCUIT TYPES OF CIRCUIT PARALLEL CIRCUIT THE CURRENT SPLITS AND DIVIDES BETWEEN EACH BRANCH IN THE CIRCUIT

AN OPENING IN THE CIRCUIT TYPES OF CIRCUIT OPEN CIRCUIT AN OPENING IN THE CIRCUIT NO CURRENT CAN FLOW

NO OPENING IN THE CIRCUIT TYPES OF CIRCUIT CLOSED CIRCUIT NO OPENING IN THE CIRCUIT CURRENT WILL FLOW

EXCESSIVE CURRENT WILL FLOW TYPES OF CIRCUIT SHORT CIRCUIT COMPONENT IS BYPASSED EXCESSIVE CURRENT WILL FLOW

TYPES OF CIRCUIT SERIES CIRCUIT Resistors are placed in a series (one after the other) Current remains constant throughout the circuit Voltage drops across each resistor

SERIES CIRCUIT RESISTOR VALUES To find the total resistance, just add up the value of each resistor R1 3Ω R3 5Ω R2 4Ω RT = R1+R2+R3 RT = 3+4+5 RT = 12 Ω Please complete exercise 3 in the assessment book.

PARALLEL CIRCUITS RESISTOR VALUES In a parallel circuit the voltage will be constant and the current flow in each branch adds up to the total current flow.

PARALLEL CIRCUITS RESISTOR VALUES There are two ways to calculate the resistance of a parallel circuit. The easiest way is to work with only two resistance values at one time and apply the formula below. RT = R1 X R2 R1 + R2

PARALLEL CIRCUITS RESISTOR VALUES Calculate the total resistance of this circuit.

PARALLEL CIRCUITS RESISTOR VALUES

PARALLEL CIRCUITS RESISTOR VALUES If there are more than two resistors, the resistance value of two at a time can be calculated and then put back into the formula. Please follow the explanation from your tutor, for the following circuit.

PARALLEL CIRCUITS RESISTOR VALUES Please complete exercise 4 in the assessment booklet.

How do we know how much work an electrical component is doing? ELECTRICAL POWER Power is the rate of doing work. This applies to electrical components as the energy stored in a battery can be converted to mechanical work in a motor (Power Dissipated). How do we know how much work an electrical component is doing?

Electrical power is said to be the product of voltage and current. Power can be calculated by using a formula, which is easy to use when a magic triangle is adopted as in Ohm’s Law. Electrical power is said to be the product of voltage and current. P = V x I

P = Power (Watts) V = Voltage (Volts) I = Current (Amps) P I V

Please complete exercise 5 in the assessment booklet. How much power is dissipated in a circuit with a motor that is drawing 7 amps? Assume that the circuit is connected to a 24 volt supply. P = I x V P = 7 x 24 P = 168 watts Please complete exercise 5 in the assessment booklet.