Download Electrical Fundamentals

IN102 - Unit5
Electrical Theories
Introduction
• Application of electrical principles is increasingly
important.
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Electrical and electronic complexity increasing
Hydrocarbons scarcer, more expensive
Increased popularity of hybrid vehicles
Investment in future technology
Introduction
• Need sound understanding of:
– Electrical terminology
– Electricity behavior
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
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
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
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.
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
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
Electrical Fundamentals—
Basic Electricity (5 of 11)
• Positive ion
– Deficiency of electrons = positive charge
– Not balanced
– Exerting attracting force on electrons
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.
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
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
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.
Electrical Fundamentals—
Basic Electricity (10 of 11)
• Insulators
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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
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
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
Electrical Fundamentals—
Electrical Circuits (2 of 3)
• Can be very basic:
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Power supply
Fuse
Switch
Component that
performs work
– Wires to connect
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.
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
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
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.
Effects of Electricity
• Electricity 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
Effects of Electricity—
Heating Effects
• May be needed:
– Circuit breakers,
heaters
• Electrical energy
transforms
– Headlights
– Defoggers
– Circuit protection
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
Effects of Electricity—
Chemical Effects (2 of 2)
• Lead-acid battery—electrical and chemical
difference causes voltage
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Makes current flow in circuit
Direct current (DC)
Same compound forms on plates.
If for too long, current stops flowing.
Recharging reverses process.
Effects of Electricity—Light Effects
• Light production from
electricity:
– LED
• Semiconductor
diode
• Light from emitting
photons when
current flows
• Produces light with
less heat, energy
• Headlights on
some cars
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
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.
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.
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.
Effects of Electricity—
Electromagnetic Effects (5 of 5)
• Electromagnetism used if component has
electrical connection and movement is created
• Devices such as:
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Relays
Solenoids
Motors
Ignition coils, transfers (to raise or lower voltage)
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
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
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.
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
Ohm’s Law and Circuits (5 of 6)
• Circuits usually fail because current too
low/none.
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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
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
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.
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
Ohm’s Law and
Ohm’s Law Calculations (3 of 7)
• Ohm’s law circle can
help determine which
math operation to use.
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
Ohm’s Law and
Ohm’s Law Calculations (5 of 7)
• Battery voltage can be measured.
– Can calculate current through every point
in circuit
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
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
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.
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.
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.
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).
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).
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.
Credits
• Unless otherwise indicated, all photographs and
illustrations are under copyright of Jones &
Bartlett Learning.