· Discuss the electrical properties of matter.
- All matter is made up of atoms.
- These atoms consist of electrons,
protons, neutrons, and the nucleus z
(center).
- Coulomb’s law says that opposites
attract, and like (the same) charges repel.
- Protons are a positive
charge, and electrons are a negative charge, each in
the nucleus.
- These attractions put the electrons in an orbit, but when they are released,
they create an electron flow, which becomes an electric current.
· Define voltage, resistance, impedance,
current, and circuits.
- Conductors: Allow the flow of
electricity through a material.
- Insulators: Do not allow the flow of electricity through a material.
- Voltage: Referred to as electromotive force, which is related to an
electrical force, or pressure, that occurs when electrons and protons
separate.
- Resistance: An opposition to the movements of electrons in materials through
which those electrons (currents) flow.
- Impedance: The collection of three characteristics
· Describe the specifications and
performances of different types of cable.
There are different factors in cable performance:
What speeds for data transmission can be reached using different types
of cable?
This is affected by the kind of conduit used, and is an extremely important factor.
The two choices for transmission of cable are digital or baseband transmission and analog-based or broadband transmission.
Will the signal from the cable weaken as it travels?
Degradation of the signal is directly related to the distance the signal travels and the type of cable used.
Some examples of cable types in Ethernet are:
10BASET – 10Mbps, the T stands for twisted pair.
10BASE5 – 10Mbps, the 5 means the signal will weaken after 500 meters. (Thicknet)
10BASE2 – 10Mbps, the 2 means the signal will weaken after 200 meters. (Thinnet)
· Describe coaxial cable and its advantages and disadvantages over
other types
of cable.
Advantages:
Coaxial can run longer distances than UTP or STP in a LAN network, without the need for repeaters. Coaxial is less expensive than fiber-optic cable, and it is a well known type of cable, used frequently for things like cable television.
Disadvantages:
Because cables must move through conduits, coaxial cables can be too rigid to install easily sometimes. Coaxial cable is more difficult to install than Twisted Pair cable.
· Describe shielded twisted-pair (STP) cable and its uses.
STP:
Shielded twisted-pair cable combines the techniques of shielding, cancellation, and twisting of wires. Each pair of wires is wrapped in metallic foil. The four pairs of wires are wrapped in an overall metallic braid or foil. (It is usually 150-Ohm cable)
Uses:
STP has much greater protection from all types of external (outside) interference, but it is more expensive and difficult to install.
As specified for use in Ethernet network installations, STP reduces electrical noise within the cable such as pair to pair coupling and crosstalk.
Testing fiber is important and there are many ways to test it. The 2 most important instruments are the Optical Loss Meter and the Optical Time Domain Reflectometers (OTDRs). They test fiber to make sure it meets the TIA standards. It also makes sure that the link power loss does not fall below the link power budget. They trouble shoot other problems that occur and they show other diagnostic information.
Discuss safety issues dealing
with Fiber Optics.
The laser light in a single mode has a longer wavelength; therefore the laser can seriously damage your eyes. Never look at the near end of the fiber that is connected to a device. Never look at a transmit port on a NIC, SITCH OR ROUTER. Always use protective covers and be very careful