1 IN102 - Unit5 Electrical Theories
2 Introduction Application of electrical principles is increasingly important. Electrical and electronic complexity increasing Hydrocarbons scarcer, more expensive Increased popularity of hybrid vehicles Investment in future technology
3 Introduction Need sound understanding of: Electrical terminologyElectricity behavior
4 Electrical Fundamentals (1 of 2)Electrical behavior is hard to understand. Must be able to visualize Governed by laws of physics Made up of tangible objects The movement of specific particles from one point to another
5 Electrical Fundamentals (2 of 2)Electricity can perform work if directed at objects that extract energy from moving particles. Moving electrical particles: Carry a negative charge Are attracted to a positive Are repelled by a negative charge
6 Electrical Fundamentals— Basic Electricity (1 of 11)All matter is made up of atoms. Each atom has a nucleus. At least one positive proton At least one neutron
7 Electrical Fundamentals— Basic Electricity (2 of 11)One or more negative electrons move around the nucleus. Travel in different rings or shells Specific maximum number of electrons Additional electrons fit into next higher ring/shell.
8 Electrical Fundamentals— Basic Electricity (3 of 11)If protons and electrons are equal: Charges cancel each other out Atom has no overall charge Electrons and protons stay balanced in the atom
9 Electrical Fundamentals— Basic Electricity (4 of 11)Negative ion Atom with more electrons than protons Not balanced and looking for a charge Electrons repel each other, push one away
10 Electrical Fundamentals— Basic Electricity (5 of 11)Positive ion Deficiency of electrons = positive charge Not balanced Exerting attracting force on electrons
11 Electrical Fundamentals— Basic Electricity (6 of 11)If negative and positive ions are close: Negative ion charge repels extra electron. Positive ion attracts extra electron. Electron is pushed from negative and pulled to positive. Both atoms are balanced.
12 Electrical Fundamentals— Basic Electricity (7 of 11)Conductors—materials that give up or accept electrons easily Insulators—materials that do not give or accept electrons easily
13 Electrical Fundamentals— Basic Electricity (8 of 11)Theories on arrangement and behavior of electronics based on atom nuclei Free electrons Located on outer (valence) ring Held loosely Free to move from one atom to another when electrical potential is applied
14 Electrical Fundamentals— Basic Electricity (9 of 11)Conductor materials allow current flow with little resistance. Most metals Copper most common in vehicles (wiring connecting components) The more electrons the conductor carries, the heavier the gauge or wire thickness needed.
15 Electrical Fundamentals— Basic Electricity (10 of 11)Insulators Most plastics Ceramics (ceramic portion of spark plugs) Electrons bound tightly to the nucleus Do not support current flow Prevent electron movement—atoms with 5–8 valence ring electrons
16 Electrical Fundamentals— Basic Electricity (11 of 11)Semiconductors—materials that conduct electricity more easily than insulators but not as well as conductors Used in transistors and microchips Atoms with four valence ring electrons Can be used as a switch
17 Electrical Fundamentals— Electrical Circuits (1 of 3)Does electrical work in controlled manner Compared to a small city: Roads—wires Stoplights—switches Businesses—electrical devices Cars—electrons that deliver workers to the workpalce
18 Electrical Fundamentals— Electrical Circuits (2 of 3)Can be very basic: Power supply Fuse Switch Component that performs work Wires to connect
19 Electrical Fundamentals— Electrical Circuits (3 of 3)Power source—potential difference measured in volts Pushes flow of electrons when switch is closed Current flows through fuse into circuit wires to produce light in a lamp. Flows through return pathway back to battery When switch opens, current path breaks and current flow stops.
20 Electrical Fundamentals— Volts, Amps, and Ohms (1 of 3)Three basic electrical measurement units Volts, amps, ohms Volts—measurement of voltage Measured with voltmeter or multimeter Hooking voltmeter across two parts of circuit Like water pressure at bottom of full water tank
21 Electrical Fundamentals— Volts, Amps, and Ohms (2 of 3)Amp—How much current is flowing at a given time when work is performed Measures number of electrons flowing in 1 sec. Starter motor—200 amps Amperage like water flowing from faucet Measured by placing ammeter into current flow
22 Electrical Fundamentals— Volts, Amps, and Ohms (3 of 3)Ohm—the amount of electrical resistance Higher resistance, less current flow Like kinking a water hose Ohmmeter measures amount of resistance. Small amount of current through part Amount of resistance changes amount the ohmmeter can push through.
23 Effects of ElectricityElectricity produces effects when it flows. May be primary reason for activity May be by-products of activity No energy transformation is 100% efficient. Waste shows up as heat. Example: Incandescent light bulb
24 Effects of Electricity— Heating EffectsMay be needed: Circuit breakers, heaters Electrical energy transforms Headlights Defoggers Circuit protection
25 Effects of Electricity— Chemical Effects (1 of 2)Chemical effects depend on ions. Ions—electrically charged atoms Gaining electrons—negative charge Losing electrons—positive charge Immersing two different metal plates in electrolyte 1 loses electrons 1 gains electrons
26 Effects of Electricity— Chemical Effects (2 of 2)Lead-acid battery—electrical and chemical difference causes voltage Makes current flow in circuit Direct current (DC) Same compound forms on plates. If for too long, current stops flowing. Recharging reverses process.
27 Effects of Electricity—Light EffectsLight production from electricity: LED Semiconductor diode Light from emitting photons when current flows Produces light with less heat, energy Headlights on some cars
28 Effects of Electricity—Electromagnetic Effects (1 of 5)Electromagnets create magnetic forces that: Attract ferrous metals and unlike charges Repel like magnetic charges Forces create mechanical movement. Creates magnetic field when current passes through a conductor
29 Effects of Electricity—Electromagnetic Effects (2 of 5)If wire is wound into a coil: Fields combine to create stronger and denser magnetic field. Has a north and south pole Magnetic field disappears when current is off.
30 Effects of Electricity—Electromagnetic Effects (3 of 5)Principles of relay Turning current on and off turns the effect into mechanical movement. Reversing current flow reverses north and south poles.
31 Effects of Electricity—Electromagnetic Effects (4 of 5)Wind conductor wire around soft iron or metal core, passing current through coil. Field strength is determined by number of coils and current flow. Metal core aligns magnetic fields to strengthen effect.
32 Effects of Electricity—Electromagnetic Effects (5 of 5)Electromagnetism used if component has electrical connection and movement is created Devices such as: Relays Solenoids Motors Ignition coils, transfers (to raise or lower voltage)
33 Ohm’s Law and Circuits (1 of 6)Explains relationship between volts, amps, and ohms Must always balance out Ohm’s law—takes 1 volt to push 1 amp through 1 ohm of resistance
34 Ohm’s Law and Circuits (2 of 6)Volts and resistance are physical things. Volts—surplus of electrons creating electrical pressure Resistance—physical restriction of conductor Amps—amount of electrons moved
35 Ohm’s Law and Circuits (3 of 6)Amps are a result of both volts and resistance. If resistance doubles and voltage stays the same, current flow is half.
36 Ohm’s Law and Circuits (4 of 6)If amps lower than they should be, possible causes: Source voltage low Voltmeter to measure source voltage Resistance in circuit too high Voltmeter to check excessive voltage drop
37 Ohm’s Law and Circuits (5 of 6)Circuits usually fail because current too low/none. Likely high resistance in feed or ground side May have too much resistance or be open Voltage drop test on both sides Resistance check for high resistance or open condition
38 Ohm’s Law and Circuits (6 of 6)Circuits are made up of components and interconnected conductors. Two basic configurations: Series circuits Parallel circuits Can combine into series-parallel circuit
39 Ohm’s Law and Ohm’s Law Calculations (1 of 7)Know two values, can calculate the third If resistance stays the same but voltage rises, greater force is needed to push more current. Total current of circuit in amps always equals voltage divided by resistance.
40 Ohm’s Law and Ohm’s Law Calculations (2 of 7)To calculate: R = resistance V = voltage A = amps Three formulas A = V/R V = A × R R = V/A
41 Ohm’s Law and Ohm’s Law Calculations (3 of 7)Ohm’s law circle can help determine which math operation to use.
42 Ohm’s Law and Ohm’s Law Calculations (4 of 7)Place finger over value to be found: If top value (volts), A × R If side values, V ÷ other value Helpful to determine current flow Do not have to break into circuit to measure current flow
43 Ohm’s Law and Ohm’s Law Calculations (5 of 7)Battery voltage can be measured. Can calculate current through every point in circuit
44 Ohm’s Law and Ohm’s Law Calculations (6 of 7)Solving Ohm’s law In example, applied voltage unknown Multiply A by R to find value of V. 6 amps × 4 ohms = 24 volts
45 Ohm’s Law and Ohm’s Law Calculations (7 of 7)Second example: Current flow value unknown Divide V by R to find A. 12 volts ÷ 3 ohms = 4 amps
46 Summary (3 of 29) Materials with many free electrons are good electrical conductors. Copper is the most common conductor. Insulators are materials that do not conduct current easily; an example is plastic.
47 Summary (9 of 29) Voltage is the electrical pressure difference between two points in an electrical circuit. The ampere (amp) is the unit used to describe how much current is flowing at a given point within a circuit when the functional component is operational.
48 Summary (12 of 29) Electrochemical energy is produced via electrolysis, which is the immersion of two dissimilar metals in a conducting liquid to break down chemicals into ions. Photovoltaic energy is produced via solar energy cells.
49 Summary (13 of 29) Piezoelectric energy is produced when certain crystals are subjected to mechanical stress. Electromagnetic induction is caused by a conductor cutting across a magnetic field. The effects of electricity include light (LED bulbs), heat (headlights), chemical reactions (lead-acid battery), and magnetism (electric motors).
50 Summary (14 of 29) Electromagnets are used in relays, solenoids, and motors, while electromagnetic induction is used in ignition coils and transformers. Relays are used to control circuits that carry high current flow; they can be normally open (NO) or normally closed (NC).
51 Summary (15 of 29) Solenoids operate similarly to a relay, but create lateral movement rather than closing a circuit. Electric motors rely on magnetic fields to create rotary movement. Ohm’s law states that the total resistance of a circuit always equals the voltage divided by the amperage.
52 Credits Unless otherwise indicated, all photographs and illustrations are under copyright of Jones & Bartlett Learning.