The Atom
A Atom is the smallest form of an element. Atoms combine to form molecules that make up all matter.
The term Electricity comes from the Greek word elektron, meaning: Amber. Amber is a fossil resin that
Ancients rubbed with wool to produce static electricity. This was their way of “shocking” someone since
they had no nylon carpet in their tents!
+N
Hydrogen Atom
Energy Levels
Each element has it’s own individual characteristics and each has a different number of electrons,
protons, and neutrons circling the nucleus. No atom has more than eight electrons in the outer shell.
This is how we have different energy levels and characteristics that are helpful in generating, conducting
and insulating an electrical current.
Orbits
Conductors
Conductors are materials with three or less electrons in the atom’s outer shell. Since these electrons are
loosely bound, they give up these electrons easily and cause current flow to occur. Copper is a good
example of an excellent conductor because it has only one electron in its outer orbit. This orbit is far
enough away from the nucleus of the copper atom that the pull or force holding the outermost electron
in orbit is relatively weak. The copper atom has 29 electrons and 29 protons.
Copper Atom
Examples of
conductors
1
2
3
4
5
6
7
What are free electrons?
NOTE: A Conductors
resistance is affected
by heat and cold.
What makes a good conductor?
Insulators
Insulators are materials with five or more electrons in their atom’s outer orbit. Because they have
more than four electrons in their outer orbit, it becomes easier for these materials to gain electrons than
to release electrons.
Examples of Insulators
1
2
3
4
5
6
Insulator Atom
How Electrons Move Through A Conductor
Electron movement through a conductor is called current. Electrons in a potential state of energy is static
electricity. When these static electrons are discharged, it becomes current flow. or kinetic electricity.
Copper Wire
-
+
(Current is the movement of electrons through a conductor.)
Flow Theory
+
-
+
-
Volts, Amps, and Ohms
Amps Discovered and named after Frenchman: André Marie Ampere (1775-1836)
1. Unit of measurement for current flow.
2. A and amps are acceptable abbreviations for amperes.
3. The capital letter I is for intensity - used in mathematical calculations.
4. Amperes is measured by an Ammeter not an ampmeter.
Volts Discovered and named after the Italian Scientist: Alessandro Volta (1745-1827)
1. Unit of measurement for electrical pressure.
2. Electromotive Force, EMF, is another way of indicating voltage.
3. The capital letter V is the acceptable abbreviation for volts.
4. The symbol used in calculations is the letter E, for EMF.
5. Voltage is measured with a Voltmeter.
Ohms The German scientist Georg Simon Ohm (1787-1854) discovered the relationship between volts amps and resistance and produced Ohms Law.
1. Unit of measurement for electrical resistance.
2. The symbol for ohms is ___, the last letter of the Greek alphabet.
3. The symbol used in calculations is the letter R, for resistance..
Ohms Law
It takes 1 volt to push 1 amp through 1 ohm of resistance.
Problem: You have decided to add a set of fog lights on your
vehicle. You have a 12V system and you know that the total
resistance of both lights is 4 ohms. What is the Amps?
Semiconductors
Semiconductors are neither conductors nor insulators. The flow of electrical current is caused by the
movement of electrons in conductors having three or less electrons in the atom’s outer orbit. Insulators
contain five or more electrons in the atom’s outer orbit and cannot conduct electricity because their atomic
structure is stable. Conductors have three or less in their atom’s outer orbit and easily give up these
electrons and cause current flow. Semiconductors are materials that contain exactly four electrons in the
atom’s outer orbit and are, therefore, neither good conductors nor good insulators.
Examples of Semiconductors
How does a semiconductor all current flow:
1
2
N-type Material
P-type Material
The Hole Theory of Current Flow
(+) Anode
P
N
(-) Cathode
Diodes
DMM Meter
Switch Code
TEMP
RPM
00.00
Hz
KHz
V
mV
A
mA
uA
M
m
K
~
_
Red
Red
Black
Red