
#19
Feb2413, 10:33 AM

P: 37





#20
Feb2413, 10:40 AM

Mentor
P: 10,864

No, it will not, there is no (significant) current flow.




#21
Feb2413, 12:10 PM

Sci Advisor
PF Gold
P: 11,398

This is turning into a nonsense scenario. Electric current is flow of charge. If there are no charges then how can there be a flow?
If you want to get more advanced then Maxwell's Equations involve the consideration of a 'displacement current' for a wave travelling through space but I don't think you are discussing at that level, are you? 



#22
Feb2413, 01:50 PM

Sci Advisor
PF Gold
P: 2,245

nitin_zilch you have been given a number of reliable responses in the first page of this thread. Stop going down a path that will destroy the prior quality of the thread Dave 



#23
Feb2413, 09:59 PM

P: 37

i want to know how electromagnetic wave is propogating and is used by the load, consider that the energy available to the load is not in from the kinetic energy of electrons? 



#24
Feb2413, 10:44 PM

PF Gold
P: 1,566

As you vary the voltage to the levels that are representing 1's and 0's. Whether that voltage is 5 volt 12 volt etc. Isnt really important.
Higher voltage is higher equates to higher current. Higher current. Signals themselves are varying levels of current. As one signal is sent then another the distance between the two signals stay the same. One does not catch up to the other. Much like sound waves travel through the air. Varying current flows the same way. The rate of current flow depends on the conductivity of the material your using. Every gate used in logic requires a certain amount of current to open the gate this is referred to in transistor logic as biasing. The key is the amount of current per given time. 



#25
Feb2513, 03:12 AM

Sci Advisor
PF Gold
P: 11,398

The conduction electrons constitute a tiny fraction of the mass of the wires (1/100,000 say) and the drift speed is around 1mm/s. Work out the KE involved. I think that you are looking for a very convenient and familiar model to describe electromagnetic effects; there isn't one. Read about it  and then read some more, if you want to get this sorted out in your head. Don't just ask more and more wild questions about it. It isn't an efficient way to learn. 



#26
Feb2613, 01:24 PM

P: 555

Back to the original question, it will be quite impossible to send full CMOSlevel (5V) signals down 100 meters of any reasonable wire at 1 Gbps. You need a SERDES (serializerdeserializer) to make this happen. Here is a good place to start if you're actually interested in digital communications:
http://www.xilinx.com/publications/a...s/serialio.pdf I suspect this was just a "theoretical" question. If so, you need to think about the concept of latency. That is, the information can still get from point a to point b but it doesn't have to be instantaneous. Thinking about electrons in a wire is usually not the most useful way to think about a digital communications link. Thinking about EM waves is usually far more fruitful. As an example of latency, we can send signals to the rover on Mars but there is a 12 minute (or so) latency (depending on orbit). But the information still gets through. How is that possible? 



#27
Feb2613, 01:39 PM

Sci Advisor
PF Gold
P: 11,398

Life is too short to think in terms of studying every link in every chain. 



#28
Feb2613, 01:52 PM

P: 555

I would say that in a serial link you would be well advised to think more in terms of eye opening rather than C/N. In a serial link it is usually dispersion that kills you, not noise. Still, if the goal is "understanding" in some sense, then EM waves are a better paradigm than discrete electrons. 



#29
Feb2613, 02:59 PM

Sci Advisor
PF Gold
P: 11,398

Electrons are probably the worst possible introduction to 'electricity'. Never touched them in my early electrical learning. Nowadays they are used by people who have very little understanding of Science to confuse kids with their teaching. And it's not even their fault.




#30
Feb2613, 03:17 PM

P: 580

On the topic of latency of data communications links here are some stats you may find interesting:
At 100 gigabit Ethernet, the spacing between bits on the fiber optic cable is a mere 2mm. A long reach (40Km) 100GBE link will contain 20 million bits in flight. Corning Glass has shipped over 30 million Km of long haul (LEAF) fiber. Thus, at any frozen moment in time, this corresponds to 15 terabits of data in flight within these cables. 



#31
Feb2613, 05:48 PM

Sci Advisor
PF Gold
P: 11,398

Latency is only a problem when synchronism is important. This can be on a circuit board where line lengths on a Bus need to be equalised to within a mm or two. 


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