BASICS OF ELECTRICITY

BASICS OF ELECTRICITY • Vocabulary • Understanding of Layer 1 & Layer 2 • Networking Professionals need a basic understanding

ATOMIC STRUCTURE • All matter is composed of atoms • Listed on Periodic Table

ATOMIC PARTS • Nucleus • Center of the atom • Protons and neutrons • Protons • Positively charged particles • Neutrons • Neutral change • Electrons • Negative charge • Orbit the nucleus

HELIUM EXAMPLE Bohr’s Model Atomic Number = 2 Atomic Weight = 4 Atomic Weight - Atomic Number = # of Neutrons 2 Neutrons 2 Protons 2 Electrons

ATOMIC SCALE • Protons & Neutrons the size of a soccer ball • Electrons the size of cherries • Nucleus in the middle of a soccer field • Electrons orbiting at the outermost seats of the stadium

COULOMB’S ELECTRIC FORCE LAW • Opposite charges attract • Like charges repel • The closer the charges come, the greater the force of attraction or repulsion

WHY DON’T THE ELECTRONS FLY IN TOWARD THE PROTONS? • The electrons have just enough orbiting velocity to prevent being pulled into the nucleus • Weak force

WHY DON’T THE PROTONS FLY AWAY FROM EACH OTHER? • Nuclear force is associated with Neutrons • Incredibly strong force which holds the Protons together

ELECTRICITY • Nuclear forces bind the nucleus together strongly • Weak force holds the electrons in orbit • If the electrons are pulled free from the atom, they can be made to flow • Electricity is the “free flow of electrons”

STATIC ELECTRICITY • Loosened electrons, negatively charged, that stay in one place • Prone to “jump” to a conductor • Leads to Electrostatic Discharge (ESD) • Usually harmless to people • Can randomly damage computer chips and/or data • Proper handling techniques essential • ESD straps, mats • handle components by non-conducting edges

MATERIALS • Atoms & Molecules (groups of atoms) • Classified by the ease with which free electrons (electricity) flow through them • Insulators • Conductors • Semiconductors

INSULATORS • Electrons flow with great difficulty or not at all • Plastic, glass, air, dry wood, paper, rubber, helium gas • Very stable chemical structures • Orbiting electrons tightly bound within the atom

CONDUCTORS • Electrons flow very easily • Best conductors are metals: copper, silver, gold • Also good conductors: solder (lead and tin) and ionized water • An ion is an atom with more or less electrons that a neutral atom • An ion is, therefore, a charged particle • Human body is 70% ionized water, so it conducts well • Outermost electrons of the atom are loosely bound and readily freed

SEMICONDUCTORS • Flow of electrons can be precisely controlled • Most important: silicon • Also carbon, germanium, gallium arsenide

ELECTRICAL MEASUREMENT TERMS • Voltage • Current • Alternating Current • Direct Current • Resistance • Impedance • Ground

VOLTAGE • Electrical pressure due to the separation of electrical charge (+ and -) • e.g. batteries • Can also be created by friction (static electricity), by magnetism (generator), or by light (solar cell) • Represented by V • Unit of measurement is volt • Definition: The amount of work, per unit charge, needed to separate the charges

CURRENT • Flow of charged particles • usually electrons • Voltage causes currents • When voltage (electrical pressure) is applied, and there is a path for the current, electrons move from the negative terminal (repelled) to the positive terminal (attracted) • Represented by I • Unit of measurement ampere (amp) • Definition: Number of charges per second that pass by a point along a path

ALTERNATING CURRENT • Current and voltages vary with time by changing polarity (direction) • AC flows from positive to negative • Polarity of terminal is reversed • AC flows in other direction • Process repeats continuously • Carried on utility power lines

DIRECT CURRENT • Always flows in the same direction • DC voltages always have the same polarity • Terminal polarities do not change • Battery power, power for microchips on the motherboard

RESISTANCE • Property of a material that opposes electrical flow • Materials with high resistance are insulators • Materials with low resistance are conductors • Amount of resistance depends on the chemical composition of the material • Represented by R • Unit of measurement is ohm (W or Ω) • Generally used to refer to DC current

IMPEDANCE • Total opposition to current flow • Analogous to resistance • General term, but applied to AC and pulsed circuits • Represented by Z • Unit of measurement is ohm (W or Ω)

GROUND • Term is used in many ways • Can mean the place on the earth that touches a building • gives electrons an extra conducting path to flow to the earth • protects your body from shock • Can mean the 0 volts reference level for electrical measurements • Voltage is created by the separation of charges • measurement must be made between two points

VOLTAGE, CURRENT, AND RESISTANCEWORKING TOGETHER • Electrons flow in closed loops called circuits • Voltage causes current to flow • Loop must be made of a conducting material • Resistance and Impedance oppose the flow of current • Using Voltage and Resistance/Impedance allows people to control the flow of a current • Multimeters measure voltage, current, resistance/impedance

GRAPHING AC & DC VOLTAGE • Oscilloscopes • Device used to study electrical signals: • X-axis represents time • Y-axis represents voltage

A SIMPLE SERIES CIRCUIT • Chemical processes in the battery cause separation of charges which provides a voltage to “push” the electrons along the conducting wire • Switch allows the circuit to be open (current flows) or closed (no current flow) • Bulb provides resistance • Electrons release energy in the form of light

GROUNDING EQUIPMENT • Outlets have two power connectors plus a safety ground connector • Safety ground wire in electrical equipment (including computing equipment) is connected to exposed metal • Prevents metal parts from being energized with hazardous voltage • Electrical current follows path of least resistance and drains off to earth • Protects body by diverting current

BASICS OF ELECTRICITY