how fast does current flow in a copper conductor. This is not a simple question.?

Answer 1

The velocity of charges in a conductor or semiconductor is called the "drift velocity". It is given by:

V= I/(n*q*A)

where I = current, n=no of charges/unit volume, q=charge, A=area of the wire.

For copper wire, n= 8.46*10^28 charges/m^3; for a 10-mil diameter wire, the result is

V=0.15 cm/sec

Not very fast!

EDIT: Note, that the speed of current flow is not the same as the speed of a signal through the wire. If you apply a pulse of current at one end of the wire it will appear at the other end after what is called the "propagation delay". This delay depends on the nature of the wire (single wire vs coax or parallel transmission line). However, from answers.com we have this information:

Propagation delay is dependent solely on distance and two thirds the speed of light. Signals going through a wire or fiber generally travel at two thirds the speed of light.

But the electrons are not travelling that fast.

Answer 2

If you are interested in the speed of a charge through the wire, this will be proportional to the applied electric field. The reason is that the charges are accelerated, then bump into something (like a phonon or another electron) which randomizes their motion--this is the source of electrical resistance by the way--and then the process repeats.

Here is a classical model of the microscopic physics.

Use the formula v=a familiar from kinematics, a is eE/m where e is the charge, m is the mass, E is the field in the wire.
The tricky part is , the average time between collisions (called the mean free time). This is related to the mean free path--how far the charge can travel in a straight line before hitting something: =/v, where is the mean free path and v is the speed of the charge carrier. So we have

v=eE/m*/v
v=sqrt(eE/m).

Answer 3

A current flowing through a wire heats it. This familiar phenomenon occurs in the heating coils of an electric range or in the hot tungsten filament of an electric light bulb. This ohmic heating is the basis for the fuses used to protect electric circuits and prevent fires; if the current exceeds a certain value, a fuse, which is made of an alloy with a low melting point, melts and interrupts the flow of current. The power P dissipated in a resistance R through which current i flows is given by

P = i2R

where P is in watts (one watt equals one joule per second), i is in amperes, and R is in ohms. According to Ohm's law, the potential difference V between the two ends of the resistor is given by V = iR, and so the power P can be expressed equivalently as

P = iV = V2/R.

You do the math.

Answer 4

You are right, it is not a simple question. It is kind of a trick question.

Electrical force transmits through the wire at 186,000 miles per second, but the actual current travels through the wire very, very slowly.

Answer 5

The answer is about the speed of light.
This can vary with the purity of the copper and temperature.

Answer 6

somewhere close to the speed of light

Answer 7

179,000 miles a second, just slightly slower than light.

Answer 8

Just have sex with it