1. 1
Fundamentals of Electricity, Magnetism, and Electronics

2. Learning Objectives Describe the structure of an atom.
Explain the relationship between free electrons and current flow.
Summarize the three basic units of electrical measurement.
Describe the characteristics of series, parallel, and series-parallel circuits.
Recall and apply Ohm’s law.

3. Learning Objectives
Explain the relationships between magnetism and electricity.
Explain the construction and operation of diodes, transistors, and silicon controlled rectifiers.

4. Matter, Elements, and Atoms
Matter is anything that takes up space and has mass
Composed of elements
An element cannot be changed into simpler material by chemical means
An atom is smallest particle of an element that can exist

5. Atoms Consist of protons, neutrons, and electrons
Structure of atom determines properties of an element

6. Electrons Travel in orbits around center of atom
Number per atom varies from one element to another
Identical in all elements
Have negative (-) electrical charge

7. Protons and Neutrons Bound together in the nucleus of atom
Protons are positively charged
Larger and heavier than electrons
Neutrons are electrically neutral

8. Characteristics of Atoms
All atoms have equal number of protons and neutrons
Electrically neutral
Held together because unlike electrical charges attract
Positively charged protons hold negatively charged electrons in their orbits

9. Characteristics of Atoms
In most atoms, nucleus is surrounded by bound electrons
Elements that contain atoms with bound electrons are insulators
In some atoms, nucleus is surrounded by free electrons
Elements that contain atoms with free electrons are conductors

10. Atoms and Electricity
Movement of free electrons will only occur when there is a complete circuit and a difference in electrical potential is produced by the source of electricity
Movement of free electrons is electric current

11. Producing Electricity
Electricity is produced in three ways
Mechanically
Chemically
Statically

12. Direct and Alternating Current
Direct Current (DC)
Produced by battery
Found in most small engine circuits
Alternating Current (AC)
Changes direction
Produced by alternator

13. Electrical Units of Measure
Ampere (A)
Number of electrons flowing past a given point in a circuit in a specific length of time
One ampere is 6,240,000,000,000,000,000 electrons flowing past a given point per second
Volt (V)
Difference in potential between two points
Ohms (Ω)
Resistance to electron flow

14. Ohm’s Law
Used to calculate unknown circuit value when other two values are known
Formula
I = E/R
where:
I = Amperes
E = Volts
R = Ohms

15. Ohm’s Law
Cover unknown value and perform calculations indicated by remaining values

16. Circuit Components Source of electricity Load Conductors
Battery or alternator (generator)
Load
One or more pieces of electrical equipment
Conductors
Connect source to load

17. Circuit Types Series circuit Parallel circuit Series-parallel circuit
One path for current
Parallel circuit
More than one path for current
Series-parallel circuit
Some devices connected in series and others connected in parallel

18. Series Circuit

19. Series Circuit Rules
Sum of voltage drops around circuit is equal to source voltage
Voltage drop is decrease in voltage as current passes through a resistance
Current is the same in all parts of circuit
The sum of the individual resistances in circuit equals total resistance of circuit

20. Parallel Circuit

21. Parallel Circuit Rules
Voltage is same in all parts of circuit
Total resistance is always less than smallest resistance
Formula for total resistance:
1/Rt = 1/R1 + 1/R2 + 1/R3…
Total current is sum of currents from each current branch
Formula for total current:
It = E ÷ Rt

22. Series-Parallel Circuit

23. Series-Parallel Circuit Rules
Determine resistance of each parallel element in circuit
Plug this resistance into circuit so circuit can be treated as series circuit

24. Magnetism
Magneto systems use magnets to generate electricity needed to fire spark plugs
All magnets produce a magnetic field
Magnetic field is strongest close to magnet
Field leaves north pole and reenters south pole

25. Theory of Permanent Magnets
Electron moving in fixed circular orbit creates magnetic field
Multiple orbiting electrons form domains
Domains scattered in random patterns in unmagnetized material
Under influence of strong external magnetic field, domains become aligned and total material is magnetized

26. Theory of Permanent Magnets

27. Properties of Magnets
Soft iron loses magnetic effect as soon as it is removed from magnetic field
Hard steel retains magnetic characteristics indefinitely
Magnetic lines of force seem to penetrate all substances

28. Magnetic Attraction and Repulsion
Lines of forces leaving the north pole of one magnet will enter the south pole of an adjacent magnet
Lines leaving similar (like) poles are repelled

29. Magnetism and Electricity
When magnetic lines of force are cut by a wire, electricity will flow in the wire
When electrons flow through a conductor, a magnetic field develops around the conductor
When current in conductor increases, the strength of magnetic field increases

30. Electrical Wire Metal conductor encased in plastic insulation
Solid or stranded
Diameter of conductor determined by amount of current it is intended to carry
Wire diameter and length determine the resistance of the wire
Wire and cable sizes expressed by a gauge number