Electrical Theory Electrical Insulators – these are material that
Electricity – it is a property of matter that results possess low conductivity or offer a relatively high
from the presence or movement of electric charge. resistance to the flow of electric current. They are
According to modern theory, matter is electrical in also called as dielectrics.
nature. Electric Semiconductors – these are materials
Structure of Matter that have conductivity about midway between good
Matter – it is anything that occupies space and has conductors and good insulators.
mass. Electrical Current
Atom – it is the smallest particle of an element that Electric Current (I) – it is the motion or transfer of
iscapable of independent existence. charges from one region of a conductor to another.
Molecule – it is the smallest particle of matter (an Its unit is the Ampere (A) named after André Marie
element or a compound) that is capable of free Ampère.
existence. Sources of Electric Current
Element – it is a substance that cannot be Static electricity from friction
decomposed any further by chemical action. Thermoelectricity is electricity from heat
Compound – it is a combination of two or more Piezoelectricity is electricity from pressure
elements. Electrochemistry is electricity from a chemical
Mixture – it is a material composed of two or more action
substances, each of which retains its own Photoelectricity is electricity from light
characteristic properties. Magnetoelectricity is electricity from magnetism
Basic Data About the Atom Fundamental Units of Electricity
Proton – it is a positively charged particle. Electric Voltage (V or E) – it is the driving force
Electron – it is negatively charged particle. behind current flow. The unit of voltage is the Volt
Neutron – it is a particle with neutral charge (no (V). Voltage level governs the amount of current
charge). flow. An increase in voltage causes more current
Atomic Number – it represents the number of flow and vice versa.
protons or electrons of an atom. Electric Current (I) – it is the motion or transfer of
Atomic Mass – it represents the sum of protons charges from one region of a conductor to another.
and electrons of an atom. Its unit is the Ampere (A).
Ion – it is an atom or a group of atoms that has a Electric Potential Difference – it is the difference
net positive or negative charge resulting from in the electric potentials of two charged bodies. Its
unequal number of positively charged protons and unit is the volt.
negatively charged electrons. Electric Resistance (R) – it is the property of a
Shell – it is an energy level or region about the material that limits the amount of flow of current and
nucleus of an atom in which electrons move. The converts electric energy to heat energy. Its unit is
atom has 5 shells, namely, the K-shell (first orbit), the Ohm (Ω).
the L-shell (second orbit), the M-shell (third orbit), Ohm’s Law
the N-shell (fourth orbit) and the O-shell (fifth orbit) According to Ohm’s Law, “At steady-state condition,
Valence electrons – is the electrons found in the the voltage across a resistor is directly proportional
outermost shell (valence shell) or orbit of an atom. to the current flowing through it with the temperature
remaining constant.”
Where: V = applied voltage in volts I = current
drawn in amperes R = resistance in ohms
Conditions for Ohm’s Law
Ohm’s law can be applied either to the entire
circuit or a part of a circuit
Electrical Classification of Materials When Ohm’s law is applied to a part circuit, part
Electrical Conductors – these are materials that resistance and the potential difference across
allow the essentially free passage of current when that part resistance should be used
connected to a battery or other source of electrical Ohm’s law can be applied to both dc and ac
energy. circuits
Limitations of Ohm’s Law • Open Circuit. If the path of current flow is
Ohm’s law is not applicable to the following: interrupted such as if the switch in a circuit is open
For metals which get heated up due to the flow of (turned off), an open circuit results.
current through them • Short Circuit. If an inadvertent shortcut develops
For electrolytes where enormous gases are in a circuit that permits current flow through an
produced on either electrode unintentional path, a short circuit is created. A
For vacuum radio valves short circuit occurs when current leaks out of the
For arc lamps intended conductor path such as out of a wire with
For semiconductors damaged insulation.
For gas-filled tubes, in which the ions are Types of Circuit Connections
generated as a result of current flow 1. Series circuit
For appliances such as metal rectifier and crystal 2. Parallel circuit
detectors, in which the operation depends on the 3. Combinational Circuit
direction of current a. Series-parallel circuit – it is a
Electrical Power combinational circuit when simplified will
Electrical Power (P) – it is defined as the rate at result into a series circuit
which electrical energy is expended or used up. It is b. Parallel-series circuit – it is a
the rate electric energy is converted into another combinational circuit when simplified will
form, such as light, heat or mechanical energy (or result into a parallel circuit.
converted from another form into electrical energy). Series Circuits
Its unit is the Watt (W). 1. Series Circuit – the circuit elements are said to be
connected in series when they all carry the same
current.
2. Properties of a Series Circuit:
The same current flows through all the
Where: resistances.
P = electrical power in watt There will be voltage drop across each
V = voltage in volt resistance.
I = current in amperes The sum of the voltage drops is equal to the
R = resistance in ohm applied voltage.
1 horsepower (HP) = 746 W 3. Equivalent Resistance of a Series Circuit:
Energy
Energy – it is the capacity to do work. It is
measured in Joules (J).
Electrical Energy Consumption – it is the rate at
which power is consumed over a specified period in
𝑾 = 𝑷𝒕
of time.
Where:
P = electrical power in watt
t = time
W = electric energy consumed
Electric Circuit
Electric Circuit – it is a collection of electrical
elements interconnected in some specific way
through which electric current flows or it is intended
to flow.
A circuit consists of a source, conducting parts,
and a load.
Closed, Open and Short Circuits
• Closed Circuit – it is an uninterrupted path that
allows a continuous flow of current through an
electrical circuit. In a building, the circuit is closed
when a switch is turned on.
