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Name: Sean
Status: student
Age: 18
Location: N/A
Country: N/A
Date: 1999 


Question:
What is the speed of electricity, in the medium of small copper wires? What is the speed of e-mail?


Replies:
The speed of a charged particle in copper is very slow: about 0.01 cm/s. At this rate, it takes about 3 hours for a charge to travel about one meter. The electric field (signal) travels at the speed of light through copper. The charge is not carrying the information, per se, but the information is transmitted by the electric field. It is like a molecule of water does not travel across the ocean, but the wave does.

Line up five hundred people. Call out, "Forward March!" They people move at about 1 m/s, but the signal that gave them the marching order was the speed of sound, or about 330 m/s. This is analogous to your question. The charge moves very slowly, but the signal is very fast.

---Nathan A. Unterman



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