Basic Concepts of Electricity
This lesson will introduce us to the fundamental knowledge of electricity. It will
enable student to be equip with the basic knowledge in electricity.
Basic Electrical Terms
Electricity is define as the flow of electron or electric current. It
is an invisible form of energy that can be transform
into other form of energy like heat light and
mechanical.
Electron is the negatively charge component of an atom. It
has the ability to flow.
Proton is the positively charge component of an atom. It
had the ability to attract electron.
Matter is anything that occupy space and has mass. It can
be a solid, liquid or gas in state.
Atom Basic component of matter. It composes of a
nucleus which is the central part, the protons and
electrons.
Current Same as electricity or flow of electron. The amount
of current flowing in a circuit can be measured in
ampere (I).
Voltage the amount of pulling force that makes the electron
flow. Also known as potential difference or
EMF(electromotive force). The amount of voltage
can be measured in volt (V).
Resistance define as the opposition to the flow of current. The
amount of resistance can be measure in ohms (Ω).
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Conductors and Insulators
Conductors are materials that easily allow the flow of current, or it has a low
resistance to current flow.
Examples; aluminum, gold, silver, copper, iron
Insulators are materials that do not easily allow the flow of current, or it has a
high resistance to current flow.
Examples; rubber, plastic, paper
Types of Current
1. Direct Current
In direct current (DC), the flow of electric charge is only in one direction. This
is the type of electricity is produced by batteries, static, and lightning. A voltage is
created, and maybe stored, until it is consumed. When the current flows directly, in
one direction. In the circuit, the current flows at a specific, constant voltage (this is
oversimplified somewhat but good enough for our needs.) When you use a flashlight,
pocket radio, portable CD player or virtually any other type of portable or battery-
powered device, you are using direct current.
Most DC circuits are relatively low in voltage; for example, your car's battery is
approximately 12V, and that's about as high a DC voltage as most people ever use.
Figure 1. Direct Current
An ideal 12 V DC current. The voltage is considered positive because its potential is
measured relative to ground or the zero-potential default state of the earth.
Direct currents flow in one direction only, and are constant in time. Their
appearance is that of a straight line which does not vary. They are produced from
power sources such as batteries, power supplies and DC generators. Photovoltaic
devices such as solar cells also generate DC power.
2. AC Alternating Current
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In alternating current (AC, also ac) the movement of electric charge
periodically reverses direction. This type of electricity is produced or generated by
AC generators commonly from a hydro electric plant. It is the commercial power that
we use in homes and offices. Delivered through a power transmission lines. AC
current can be reduced through the use of power transformer to suite for its
application. It can also be converted to DC for a specific purpose. In the Philippines
AC is rated as 220V AC at 60 Hz.
Alternating currents change direction, flowing first one way and then the other.
They are sinusoidal waves, so that they change in time. They are produced from
sources such as power supplies and AC generators. In North America, AC is 120
volts and 60 hertz or cycles per second. This means it changes direction 60 times
per second. In Europe, it is generally 50 hertz with 220 to 240 volts.
Figure2. Alternating Current
Why does standard electricity come only in the form of alternating current?
There are a number of reasons, but one of the most important is that a characteristic
of AC is that it is relatively easy to change voltages from one level to another using a
transformer, while transformers do not work for DC. This capability allows the
companies that generate and distribute electricity to do it in a more efficient manner,
by transmitting it at high voltage for long lengths, which reduces energy loss due to
the resistance in the transmission wires. Another reason is that it may be easier to
mechanically generate alternating current electricity than direct current.
PC’s use only direct current, which means that the alternating current
provided by your utility must be converted to direct current before use. This is
the primary function of your power supply.
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AC POWER PC’s PSU DC POWER
MOTHERBOARD
DRIVES
COOLING FANS
Figure 3. Simplified block diagram of a PC power supply
Electric Circuit
Electric circuit - is the pathways for electricity to flow.
Components of Circuit
Load - commonly represented by a bulb or any electrical component that
consumes electricity.
Supply - Commonly represented by a cell or a battery
Switch - an electrical device that opens or closed a circuit.
Load
Supply
Switch
Figure4. A simple circuit
Types of Circuit
1. Open Circuit - a type of circuit that has an open path for current to flow. It means
that current cannot flow in open circuit.
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Load
- +
Supply
Switch
Figure5. An open circuit
The switch is said to be “OPEN” the current can’t flow into the circuit and the
bulb is “OFF”
2. Closed Circuit - a type of circuit that has a closed path for current to flow. It
means that current can flow in a closed circuit.
Load
- +
Supply
Switch
Figure 6. A closed circuit
The switch is said to be “CLOSED” the current can’t flow into the circuit and
the bulb is “ON”
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