Module-1

Classical Theory – Flow of Electrons

Electrons in an orbital shell near the nucleus have a strong attraction to the protons in the nucleus and thus are difficult to free. Electrons in outer orbital shells experience a weaker attraction and are more easily freed.

Modern Theory – Flow of Charged Particles

Electricity is tied to even smaller subatomic particles that possess either a positive or negative electromagnetic charge. Not all subatomic particles have a charge. It is only the subatomic charged particles, those with an electromagnetic charge, that are associated with electricity.

Law of Charges

Opposite charges attract each other, and like charges repel each other. When an atom has an equal number of electrons and protons, charges cancel, and the atom is electrically neutral.

positively charged.

An atom containing fewer electrons than protons

negatively charged.

An atom containing more electrons than protons

positive ion

positively charged atom.

negative ion

negatively charged atom.

Electrical Current

A flow of electric charge through a conductor is an electrical current or, simply, current.

Electricity

the flow of current through a conductor.

Static electricity from friction

Rubbing two materials together produces a charge of static electricity. Heat energy caused by friction frees electrons near the surface of one material, and they move to the other material.

Thermoelectricity

Electricity from heat. When two dissimilar metals are joined, a thermoelectric charge is created when the joined metals are heated. This device is called a thermocouple.

Piezoelectricity

Electricity from pressure. Certain crystalline materials produce a piezoelectric charge when a force deforms or strains the material.

Electrochemistry

Electricity from a chemical reaction. A galvanic reaction produces opposite electrical charges in two dissimilar metals when placed in certain chemical solutions.Electrochemistry is the study of the relationship between electricity and chemical reactions, where chemical energy is converted into electrical energy.

Photoelectricity

Electricity from light. When photons strike a material, they release energy that can cause atoms to release electrons.

Magnetoelectricity

Electricity from magnetism. A moving conductor in a magnetic field induces electron flow.

Conductors

Carry electrical current with minimal resistance (e.g., copper, aluminum, gold, water).

Insulators

Resist the flow of electricity (e.g., rubber, glass, ceramic).

Semiconductors

Behave like conductors at high temperatures and insulators at low temperatures.

Voltage (V)

Electrical pressure that moves current in one direction.

Current (A)

Rate of current flow, measured in amperes.

Resistance (Ω)

Opposition to current flow, measured in ohms

Ohm’s Law

V = IR

Power (W)

Rate at which work is done: P = VI

Energy (Wh)

Power consumed over time: E = Pt

Electric Circuit

an interconnection of electrical elements linked together in a closed path so that an electric current may flow continuously. also called electric network.

Branch

may be composed of one or more elements in series

Node

point wherein 2 or more branches meet

Loop

interconnection of branches forming a closed path

Series Circuit

Same current, additive resistance.

Parallel Circuit

Same voltage, additive reciprocal resistance.

Kirchhoff’s Current Law (KCL)

The sum of currents entering a node equals the sum of currents leaving the node.

Kirchhoff’s Voltage Law (KVL)

The sum of voltage drops and voltage rises in a closed loop is equal to zero.

induction

When a conductor moves through a magnetic field, or when a magnetic field moves across a conductor, a voltage is induced, causing current flow.

DC (Direct Current)

Current flows in one direction. [elevators, escalators]

Alternating Current (AC)

Current direction continuously changes. [power sources e.g. outlets]

Cycle

One complete change from one direction to the reverse and back.

Frequency

Cycles per second, measured in hertz (Hz)

Philippine standard frequency

40 Hz; voltage 230V ±15%.

Ideal Transformer

Transfers AC voltage and current from one circuit to another through induction.

Inductors

Store energy in an electromagnetic field; cause current to lag voltage in AC circuits.

Capacitors

Store energy in an electrostatic field; cause voltage to lag current in AC circuits.

Impedance (Z)

Total opposition to AC current due to resistance, inductance, and capacitance.

Real power (W)

Performs useful work.

Reactive power (VAR)

Generates the magnetic field for inductive devices.

Apparent power (VA)

Total power drawn by a circuit.

Demand charges

Imposed for peak power consumption; reduced through load shedding, load shifting, peak shaving, and Time-of-Use (TOU) rates.

Load Shedding

Non-essential loads are switched off to maintain a uniform load, thus limiting demand.

Load Shifting

Moves non-essential loads to periods of low demand to reduce peak power consumption.

Peak Shaving

Uses energy storage and alternative energy sources to reduce peak demand.

Time-of-Use (TOU) Rates

A pricing structure that rewards consumers for reducing power consumption during periods of high electrical demand.