How does the physical layer interference work in a computer network?

Solution 1:

How much time have you got? Seriously, this is a major topic but also one that's the subject of many standards and so doesn't really rely on someone here using their specific knowledge to write up something that is well documented elsewhere.

if you want to start with some serious basics, look up the OSI 7-layer model that defines the various functions performed by two entities communicating across some form of network media, and then zoom in on the physical layer where all the data transmission and reception takes place - below are some references. I expect this is the best you'll get here unless someone takes a long time to document what you need OR the question is closed as it's not really answerable here. The last link on CSMA/CD may help you understand how one form of multiple media access works.

7 layer model:

http://en.wikipedia.org/wiki/OSI_model

http://www.networkdictionary.com/protocols/osimodel.php

Physical layer data transmission (over twisted pair copper):

http://en.wikipedia.org/wiki/Ethernet_physical_layer

CSMA/CD

http://www.erg.abdn.ac.uk/users/gorry/eg3561/lan-pages/csma-cd.html

Solution 2:

Here is an article from Rice University explaining how NICs work, specifically a 10 Gbps NIC.

Solution 3:

But question is, if there're many other NICs connected to a shared wire, will the electric current be weakened?

I don't think there is or needs to be a lot of current: Ethernet works at radio frequencies.

But yes, I think it will be weakened. A "shared wire" might be the same thing as a "passive hub": I guess there's a limit to the number of ports in a shared hub (like there's a limit to the length of a cable).

So if you have many other NICs, you'd have an active hub or a router.