BASIC CONCEPTS OF ELECTRICITY

Computer Hardware and ServicingLesson 4, Module 4

MA. RACHEL B. ESPINOBuhatan National High SchoolPurok Marcos, Buhatan, Sorsogon City

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.

Basic Electrical Terms

Electron is the negatively charge component of an atom. It has the ability to flow.

ELECTRON

Proton is the positively charge component of an atom. It had the ability to attract electron.

PROTON

Matter is anything that occupy space and has mass. It can be a solid, liquid or gas in state.

MATTER

Atom is the basic component of matter. It composes of a nucleus which is the central part, the protons and electrons.

ATOM

Current same as electricity or flow of electron. The amount of current flowing in a circuit can be measured in ampere (I).

CURRENT

Voltage is 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).

VOLTAGE

Resistance is define as the opposition to the flow of current. The amount of resistance can be measure in ohms (Ω).

RESISTANCE

Conductors are materials that easily allow the flow of current, or it has a low resistance to current flow.

Examplesaluminum, gold, silver, copper, iron

CONDUCTORS AND INSULATORS

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

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. The current flows directly, in one direction.

1. DC (Direct Current )

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.

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.

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

2. AC (Alternating Current)

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.

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.

Why does standard electricity come only in the form of alternating current?

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.

Simplified block diagram of a PC power supply

Electric circuit - is the pathways for electricity to flow.

Electric Circuit

1. Load - commonly

represented by a bulb or any electrical component that consumes electricity.

2. Supply - Commonly represented by a cell or a battery

3. Switch - an electrical device that opens or closed a circuit.

Components of Circuit

A simple circuit

SUPPLY

LOAD

SWITCH

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.

Types of 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.

The switch is said to be “CLOSED” the current can flow into the circuit and

the bulb is “ON”

Identify what is being described in the following statements.

QUIZ