CS485 Sylabus

### Transmission over a copper wire

• Energy loss in signal transmission in copper wires

• Physics:

 When an electrical signal (= electricity) traverse through a copper wire, the always lose some power

Graphically:

Terminology:

 Attenuation = loss of power

• Source of power loss

• There are 2 ways that an electrical signal can lose power:

• Resistance (in the wire):

Resistance in the wire will cause some of the energy in the signal to be converted into heat

When the frequency of the electric current is very high, an alternating current will generate a strong electro-magnetic field.

The wire will work like an antenna - and some energy of the signal will radiate away....

• Fact from Physics:

• The amount of power loss depends on:

 The resistance of the transmission medium The frequency of the electro-magnetic signal (= how much of the power will radiate away).

• Energy loss characteristics

• The energy loss characteristics is as follows:

• When the (alternating) electric current has a very low frequency:

 the current encounters high electrical resistence. (DC current generates a low of heat !!!!)

Result:

 A large portion of the energy in the transmitted signal is lost because the energy is converted into heat

• When the (alternating) electric current has a very high frequency:

 the current will generate a strong electro-magnetic field.

Result:

 A large portion of the energy in the transmitted signal is lost because the energy is converted into electro-magnetic wave (radiation)

• Energy loss characteristic of a wire transmission medium is as follows: