Networking media
From Mycomputer Notes
This chapter deals with the media used to connect devices into the network. OVer here the term media, refers to what we used to connect the networking devices, the cable.
Based on the OSI Model we know that the Pysical Layer is the one responsible for transfering data (text, pictures, audio) between the source and the destination. Data that travels between the source and the destination is represented by the presence of electrical pulse. It represented by an electrical pulse if the media been is used is a wire, copper, or light pulses in in optical fibers.
In today network environment the most popular type of media is a type of cable composed by copper and the type of signal that travels through this copper wire is a electrical signal.
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[edit] Copper Media
This chapter instroduces some basic theory of electricity to better understand Networking at the Layer 1 Level (Physical Layer) of the OSI Model. Like any other element from the Periodic Table of Element Copper has it own properties:
The basic unit of all matter, including copper, in the universe is the atom. An atom is made of threee tyny particles: Protons (particles positivelly charge) Neutrons (particles that have not charge) Electrons (particles that a have a negative charge)
[edit] Electrical Properties of Matter
Atoms normallly have a equal number of protons and electrons. Atoms bond together in different combinations to form molecules of various types of matter.
The nucleus of a atom is bound together by a powerfull force. The electrons on the nucleus are bound together with much weaker force. Since this force is much weaker certain electrons can be pulled away and orbit around nearby atoms. This movement of electrons is definied as Electrical Current
Explainning how the movement of one electron changes the molecules of the atom therefore changing the nature of the matter (Atom) is out of scope for this Article. But we can tells you that Atoms and molecules are classified as belonging to one of the threee groups:
- Insulators
- Conductors
- Semiconductors.
| Material | Flow | Examples |
| Insulators | Electrons flow poorly | Plastic, paper, rubber, dry wood, air, pure water and glass |
| Conductors | Electrons flow well | Copper(CU), Silver(Ag), Gold(Au),Water with ions and Human body |
| Semiconductors | Electrons flow can be controlled precisely | Sillicon (Si), Carbon, Germanium(Ge), Gallium Arsenide (GaAs) |
So far we have stablished that Copper is an excellent Electrical conductor. But we need to measure the electricity that travels through the wire to be able to used it. Electricity can be measure in numerous ways, but in this section and thosed that follow , will focus on
- Voltage
- Current
- Resistance
- Impedance
[edit] Voltage
Is the forced generated by the separation of an electron and proton. The forced created pulls toward the opposite charge and pushes away from the like charge. The seperation of charges results in voltage Voltage can be created by friction, by nagnetism or by solar energey.
Voltage is represented by the letter V and the Unit of measurement is is the volt. Two kinds of voltage exits:
- Direct-current (DC)
The movement of electrons in a DC circuit is always in the same direction, from negative to positive. A battery is an example of a DC voltage.
- Alternative-current (AC)
In a circuit, the positive and negative terminals of the C volatage change to negative and positive back and forth. This change makes the direction of electrons movements change, or alternate, with respect of time.
[edit] Resistance and Impedence
Resistance is the property of a material that resists electron movement, Conductors have low resistance and insulators have high resistance Resistance is represented by the letter R and the unit of measurement is ohm.The term resistance is generally used when referring to DC circuits. The resistance to the movement of electrons in an AC circuit is called Impidence. Impidence is represented by the letter Z and the unit of measurement is the ohm.
[edit] Current
Electrical current is the flow of charges that is created when electrons move. Whe electrical pressure (voltage) is applied and a path for the current exits, electrom move from the negative terminal (which repels them), long the path, to the positive terminal (which attract them). Current is represented the letter I. The unit of measurement for current is ampere and it is represented by the letter A, or amp.
- Amp
- Is the number of charges per second that pass by a point along a path or in other words the amount of electron traffic is flowing through a circuit.
[edit] Wattage
The combination of amperage(quantity of electrons past a given point) and voltage (pressure or speed of electrons ) equals Wattage or electrical power. A watt (W)is the basic unit of electrical power. Wattage equals voltages times amperage (W=V x I)
