flow of current?

Question

Once I was watching on a tv how the currenct flow in a wire. A scientist who was describing this told that the current flows without a delay. Is it true?? If yes where I can find the information about it???

Answer 1

Yes, it is true. When you look at current flow, you can't just look at the flow of one electron. The wire is full of electrons. Current flow without delay just means ALL of the electrons start moving at the same time. In other words, you don't have to wait for an electron to get from the battery's negative terminal to the positive terminal. As soon as one electron is leaving the negative terminal, a different electron is entering the positive electron.

And the term 'without delay' is kind of a fuzzy term. Technically, there is a slight delay. An electron will enter the positive terminal before one leaves the negative terminal. When an electron enters the positive terminal, a 'hole' is left behind - in other words, you have a positively charged atom left behind that attracts a new electron to fill its slot. That ripple effect - leave a hole, fill a hole leaving another hole further down the wire, travels down the wire a whole faster than any single electron moves. The effect, what's considered the current flow, travels the entire distance of the wire, while a whole bunch of electrons have moved a very tiny distance.

The current flow is less than the speed of light, though. It's actual speed depends on what the wire is made of, the types of components in the circuit, temperature, and so on, so it's hard to put a general number to the speed. I think the flow for most circuits, like the electrical wiring in your house or the current through your TV, is around 1/6 the speed of light.

Answer 2

Electrons in a metal do not flow at the drift velocity. The drift velocity is derived by assuming all the free electrons contribute to the electrical current, where the current density, j, is given by:

j = n e vdrift

where n is the density of free electrons, e is the electric charge, and vdrift is the drift velocity.

In reality, n is not the the density of free electrons, but a small fraction of the density of free electrons. This comes from quantum mechanics that only allow a small fraction of the available electrons to contribute to the overall transport. Once the corrected value of n is put in, since it is much smaller than for all the free electrons, and since j is constant, the velocity must increase. This velocity is called the Fermi velocity, and is typically about 1 - 10% of the speed of light.

Hence, the answer is there is a delay in current associated with the time it takes the current to flow through the circuit. The electron speed is given by the Fermi velocity.

I hope this helps.

Bozo

Answer 3

It is funny, that the electons, which carry the current just have typical drift velocities in conductors of about a few centimeters per second. But the electric field, wich causes the force on the electron and thereby thier motion travels with the speed of light. So the "start signal" to move goes through the conductor with the speed of light, which then all begin to accelerate nearly simeltaneuos. But then they colide with impurities in the conductor and do other things which limits thier speed and in the averaged result you get this above mentioned low drift speed.

The basics of this process is described in every book about solid state physics, but the exact methods how to calculate the voltage current characteristics of a given system is still subject to actual research.

Answer 4

Current does not flow at the speed of light. ELECTRIC FIELD FLOWS BY THE SPEED OF LIGHT.
In fact the carriers of current ,the electrons flow at a very slow pace of few centimeters/sec, which is called drift velocity.

CURRENT FLOWS WITHOUT A DELAY BECAUSE OF THE INSTANTANEOUS ACTION OF THE ELECTRIC FIELD ON THE CURRENT CARRIERS the electrons

The drift velocity is the average velocity that a particle, such as an electron, attains due to an electric field. Since particles can accelerate arbitrarily close to the speed of light in the absence of other forces, the term "drift velocity" can only really apply to carriers in materials, and not to particles in a vacuum. Particles in solids, for example, actually collide or scatter with the crystal lattice (or phonons), which slows them down. Drift velocity is non-uniform as it involves electric field as an externally accelerating agent.

Answer 5

assuming current just flows along a wire in a dc system then it should flow non stop at the speed of light

Answer 6

is delay the same as resistance? if you have a bulb in the equation then the resistance is higher if it is just wires with separate paths then there is much less resistance i think that is what he was saying??

Answer 7

Check out the link below. it will help explain it.