Electricity is an energy that originates from the positive charge (+) and negative charge () of atomic nuclei, which are contained in all elements. Like other energies, electricity also has the characteristic of being conducted from one location to another. Put simply, electricity can be defined as an invisible flow of energy
Module Basic Electronics & Electricity Learning Objectives Describe the basic concept of electrics and electronics Understand circuit diagram components and be able read circuit diagrams Explain communications modes used in vehicles Use inspection tools and diagnostic equipment appropriately Electricity and Magnetism 1.1Electricity 1.2Current 1.3 Voltage and Resistance 1.4 Network Analysis 1.5 Electric Power and Electric Power Level 1.6 Magnetism 1.7 Alternating Current 1.8 Semiconductor 1.9 Diode and Transistor 1.10 Sensor Circuit 2.1 Basic Circuit Knowledge 2.2 Circuit Analysis Communication 3.1 Outline of Communication 3.2 Automotive Electrical Communication Tools & Equipment 4.1 Safety Sign & Advice 4.2 Multi Meter Use 4.3 Use of GDSas Diagnostic Equipment Electricity and Magnetism 1.1 Electricity Electricity is an energy that originates from the positive charge (+) and negative charge (-) of atomic nuclei, which are contained in all elements Like other energies, electricity also has the characteristic of being conducted from one location to another Put simply, electricity can be defined as an "invisible flow of energy." 1) What is an electron ? All metals are made up of electrons It is one of the different particles that make up an atom As the moon circles the earth, electrons circle the center of an atom The center of an atom is called a "core."A core comprises protons and neutrons An electron is negatively charged, a proton is positively charged and a neutron is neutral In metals, some of the electrons circling the atomic nucleus is loosely connected to the nucleus Such electrons are called "free electrons", and Fthey are capable of moving from one atom to another It is the movement of free electrons that create a flow of electrons With increased temperature, the movement of electrons is made more rigorous This flow of electrons can be defined as "electricity." 2) Movement of Electricity An object with gathered electrons is referred to as being "negatively (-) charged" and an object without electrons is referred to as being "positively (+) charged." When a negatively charged object is connected to a positively charged object by a conductor, the excess electrons in the negatively charged body move to the positively charged body and reduce the latter's electron shortage As the diagram on the right shows, electrons ejected from a cell collide with the electrons of the conductor wire The collision causes a single free electron to be ejected from the conductor atom, and the electron space in the conductor atom made vacant becomes filled by a cell electron Electrons that reach the very end of the conductor wire enter the positive polarity of the cell "Electric charge" is the basic unit of electrical movement The flow of electric charge continues until there is no difference in the electric charge of (+) and (-) 10 1.2 Current 1) What is a current? As explained earlier, connecting a negatively charged object with a positively charged on results in electrons moving from (-) to (+) In such an instance, it is said that a "current flows" in the conducting wire As such, currents are formed by the movement of free electrons The volume of electric charge movement is referred to as a "current." However, the direction of current flows is not the same as the direction of electron flows As the direction of a current is defined as the direction of (+) electricity, current direction is the opposite of electron direction 2) Action of a Current Heat Generation When a current flows through a conductor wire, there is a limit to the current volume the wire can consistently maintain If such that limit is exceeded, heat is generated in the wire This is due to a flow of more currents than what is allowed The light bulbs, lighter and heating wire in vehicles use the heat generated by currents Placing copper and zinc in diluted sulfuric acid causes the ionization of said metals Here, the copper will undergo an electron shortage and become positively charged, while the zinc undergoes an electron excess to become negatively charged Connecting a conducting wire to these two polarities moves the electrons of the zinc to the copper, thus creating a current Car batteries take advantage of this chemical action Chemical Action Magnetic Action Ground metal Thick paper (+) (-) Make a hole in a thick piece of paper, put a conducting wire through it, and create a current before sprinkling some ground metal over it The ground metal will form a concentric circle around the conducting wire, and end up on the surface perpendicular to the conducting wire This is because a magnetic field was created by the magnetic action of the current Likewise, a coil made from a conducting wire that has a flowing current creates a magnetic field This is constitutes the basic mechanism of a motor The ignition coil, starter motor, wiper motor and alternator of a vehicle use this magnetic action of currents to function 11 1.3 Voltage and Resistance 1) What is voltage? When a current flows through the circuit as shown in the diagram, the light bulb is lit The capacity of energy consumption that takes place in a current-flowing circuit is referred to as "voltage." A current continues to flow until the electric potential difference at the two ends of the conductor becomes A device designed to maintain such an electric potential difference is a battery or power supply device As such voltage can be defined as an "electric potential difference that makes a current flow through a circuit." 2) Serial and Parallel Circuit of Cells Serial circuit : Cells are connected in a line Total voltage is the sum of each cells' voltage Parallel circuit: Cells are connected parallel to each other Total voltage equals the voltage of a single cell 3) What is resistance? A vehicle is unable to pick up its speed on an unpaved road that is bumpy or muddy The road surface hinders the vehicle from doing so Similarly, the property that hinders the flow of electrical currents is defined as "resistance." Conductor wires are designed to promote current flow, but at the same time exert resistance against current flow; so low-resistance wires are more efficient In some instances, a channel through which a current travels must have resistance, i.e the filament of a light bulb Conducting wire resistance R R= ρ·S/l l: Conducting wire length(m) S: Conducting wire cross ection(m)² ρ: Conductor resistance rate(Ω·m) The electrical resistance of a resistant body, such as carbon or metal, is marked by wrapping a nonconductor around the resistant body and placing a colored band The type shown in the photograph is primarily used for small currents that are less than 1A If larger currents are required, the size must be increased to withstand the heat generated from resistance 12 1.4 Circuit Theory (a) shows three light bulbs connected to one 1) Ohm's law cell, and (b) shows one light bulb connected to two cells The light light bulb in (b) will light up brighter According to Ohm's law, the size of a current flowing through a conductor is proportional to the voltage at the two ends of the conductor, and inversely proportional to resistance (light bulb) (a) I(Current) = V(voltage)/R(resistance) (b) V(Voltage)=I(current)·R(resistance) 2) Serial and Parallel Circuit of Resistance Serial circuit The size of total resistance in a serial circuit can be calculated by combining all resistances R = R1 + R2 + R3 , according to Ohm's law, the current is I = V/R = V/(R1 + R2 + R3) Parallel circuit In a parallel circuit, where the two ends of two or more resistances is connected to a single source, the total size of resistances can be calculated as follows 1/R = 1/R1 + 1/R2 + 1/R3, according to Ohm's law, the current is I = V·(1/R1 + 1/R2 + 1/R3) Comparison Serial circuit Parallel circuit Voltage The voltage of each element varies by the element's resistance, the total of all elements' voltage equals the total circuit voltage As all elements are connected to a single set of two points in a circuit, the voltage of each element equals the total voltage of the circuit Current Being connected via a single conducting wire makes the current flowing through each element equal to the circuit's total current A circuit's total current is divided at the parallel junction and varies according to the resistance of each element The total of all elements' currents equals the circuit's total current If one light bulb gets disconnected, the circuit becomes cut off and no current flows Even if one light bulb gets disconnected, the others are not affected Connecting the light bulbs in a serial circuit increases total circuit resistance, reducing the brightness of each light bulb Connecting the light bulbs in a parallel circuit does not subject the current to total circuit resistance, so there is no change in the brightness of bulbs Interresistance relationship 13 3) Kirchhoff's law Kirchhoff's law is a theory that wholly reflects the characteristics of a serial circuit and parallel circuit explained earlier Kirchhoff's first law addresses currents and the second law voltage Kirchhoff's first law The sum of currents flowing in matches the sum of currents flowing out Voltage applied to a parallel circuit by power supply makes a current flow in each resistance However, total currents in the circuit gets divided at the parallel junction to flow inversely proportional to each resistance Circuit's total currents I = (1/R1 + 1/R2)·V = (1/2 + 1/5)·10 = 7A I1 = V/R1 = 10/2 = 5A, I2 = V/R2 = 10/5 = 2A → I = I1 + I2 If 7A flows through the circuit, 5A flows against a resistance of ohm and 2A flows against a resistance of ohm to make the current total 7A again Kirchhoff's second law The total of voltage drops occurring in a closed circuit equals the electromotive force (voltage of the power supply device) of the circuit Creating a flowing current in an electrical circuit with resistance results in the circuit's voltage decreasing by the level of voltage at the two ends of the resistance This is called a voltage drop The voltage of power supplied to a serial circuit is divided proportional to the resistance of each element and consumed In short, a voltage drop occurs for each resistance Total voltage of a circuit V = I·R1 + I·R2 + I·R3, I = R/V = (R1 + R2 + R3) / V = (2 + + 5)/10 = 1A V = + + = 10 → V = V1 + V2 + V3 A voltage drop of 2V occurs for a resistance of ohm, 3V for a resistance of ohm and 5V for a resistance of ohm The sum of all voltage drops equals the total electromotive force of 10V 14 1.5 Electric Power and Electric Power Level 1) What is electric power? Moving electric charge generates heat in a circuit or drives a motor A flowing current changes electric energy into another energy; the ratio of this change is referred to as "electric power." Electric power equals the multiplication of voltage and current Electric power (P) = Voltage ( V) X Current (I) , the unit W(watt) is used 2) What is an electric power level? Electric power level is calculated by multiplying electric power by time Electric power that remains constant results in increased electric power consumption over time Electric power level (W) = Electric power level (P) X Time (t) = Voltage (V) X Current (I) X Time (t) , The unit Wh(watt-hour) is used 3) Fuse Use A device that automatically cuts off currents in a wire that are in excess of an allowed limit Overcurrents generate heat that melt and disconnect fuses In the diagram on the left, (a) is the part with the heaviest current flow A fuse is (c) 220V-50W installed in (a) for this reason If all the electrical products in the diagram were used, how much current flow will take place in the fuse? (b) 220V-100W P = V·I , I = P/V I = 500/220 + 100/200 + 50/220 = Approx 2.95A As such, a fuse that allows a maximum (a) current flow of 2.95A and higher must be 220V-500W installed In general, a fuse's maximum allowed current is 1.2 to 1.5 times that of the used current 15 1.6 Magnetism 1) What is magnetism? Magnetism is the force magnets that pulls in materials and forms the basis of actions that take place between two magnets or between a magnet and current A magnetic field is always present where currents flow Ampère's law Groun d metal Thick paper (+) (-) Magnet When a conducting wire with a flowing current is grabbed with the right hand with the thumb pointing in the direction of the current, a magnetic field forms in the direction of the other fingers Ground metal placed around a current-flowing conducting wire lines up in a set direction - the same direction as the one in which a magnetic field forms when a conducting wire is gripped This is "Ampère's law." A magnet is a magnetic object Magnets are categorized into permanent magnets and electromagnets The rotor coil in a motor, rotor coil in an alternator, and a solenoid coil use an electromagnet that becomes magnetic temporarily when a current flows through it Fuel pumps and wiper motors use both permanent magnets and electromagnets What is a magnetic field? An area in which magnetic force is exerted is called a magnetic field For example, the area around a magnet in which metals are pulled in toward the magnet is a magnetic field The Right-hand screw rule Four fingers: Current direction Circular Loop Conductor Direction of Current Thumb: Magnetic field direction Direction of Current Current(I) Right-hand Current(I) Forming a circle with a conducting wire and flowing a current through it creates a magnetic line of force that penetrates the surface created by the circular current Here, turning the right-hand screw in the direction of the current sets the right-hand screw's progressive direction as the magnetic field direction An examination of a magnetic field formed by a coil is as follows A solenoid coil is a conducting wire wound tightly in a cylindrical shape Applying the right-hand screw rule, turning the righthand screw in a current's direction changes the magnetic field's direction from right to left Another way of understanding this concept is gripping a coil with the right-hand with the four fingers in the direction of current flow; it can be observed that a magnetic field forms in the direction of the thumb 16 Mechanism of a relay A relay is an electronic part used for driving and signaling electrical/electronic products, and is widely used in vehicles also Flowing a current through an iron core wrapped with a coil makes the iron core an electromagnet that pulls in a steel plate to close the switch on the steel plate This mechanism of a relay is used to open and close circuits 1.7 Alternating Current 1) What is an alternating current? (a) Direct current (b) Alternating current Current Current Current direction Current direction Time Time A direct current is represented as "DC." It is a current that flows in a single direction, i.e from (+) to (-) Because the terminals of a battery always maintain the same polarities, currents only flow in a single direction in an electrical circuit On the other hand, an alternating current is represented as "AC." Alternating currents flow in no set direction, i.e current direction alternates The reason for this is constantly changing voltage 2) Alternating current generation Magnetism is always present where electricity is Magnetism is formed by a conducting wire with a flowing current Also, electricity can be generated by magnetism Faraday and Henry made the discovery that placing a magnet in and out of a coil creates a current flow in the conducting wire Inducing voltage in a coil Change the volume of a magnetic field in a coil • Move a coil in close proximity to a magnet • Move a magnet in close proximity to a coil • Change the current flowing in another coil in close proximity to a coil Induced voltage increases when the number of copper conducting wires moving within a magnetic field increases or if the speed at which a magnetic line of force goes in and out of a coil increases 17