In an electric current, do electrons travel close to the speed of light?

Answer 1

When free electrons move, there is a net flow of charge, this flow is called an electric current. The drift velocity of electrons in metal wires is slow.

(The drift speed of electrons in a copper wire is something around 0.0043 m/s.)

However, the speed at which a current at one point in a wire causes a current in other parts of the wire is typically 75% of light speed.

(light speed c = 3 x 10^8 m/s)


Detailed Explanation:

The Nature of Charge Flow

The average drift speed of an electron is very, very slow, the question soon arises: Why does the light in a room or in a flashlight light immediately after the switched is turned on?

Wouldn't there be a noticeable time delay before a charge carrier moves from the switch to the light bulb filament?

The answer is NO! and the explanation of why reveals a significant amount about the nature of charge flow in a circuit.

Charge carriers in the wires of electric circuits are electrons. These electrons are simply supplied by the atoms of copper (or whatever material the wire is made of) within the metal wire. Once the switch is turned to on, the circuit is closed and there is an electric potential difference established across the two ends of the external circuit. The electric field signal travels at nearly the speed of light to all mobile eelectrons within the circuit, ordering them to begin marching. As the signal is received, the electrons begin moving along a zigzag path in their usual direction. Thus, the flipping of the switch causes an immediate response throughout every part of the circuit, setting charge carriers everywhere in motion in the same net direction. While the actual motion of charge carriers occurs with a slow speed, the signal which informs them to start moving travels at a fraction of the speed of light.

The electrons which light the bulb in a flashlight do not have to first travel from the switch through 10 cm of wire to the filament. Rather, the electrons which light the bulb immediately after the switch is turned to on are the electrons which are present in the filament itself. As the switch is flipped, all mobile electrons everywhere begin marching; and it is the mobile electrons present in the filament whose motion are immediately responsible for the lighting of its bulb. As those electrons leave the filament, new electrons enter and become the ones which are responsible for lighting the bulb. The electrons are moving together much like the water in the pipes of a home move. When a faucet is turned on, it is the water in the faucet which emerges from the spigot. One does not have to wait a noticeable time for water from the entry point to your home to travel through the pipes to the spigot. The pipes are already filled with water and water everywhere within the water circuit is set in motion at the same time.

Answer 2

Electric Current Speed

Answer 3

No, the electrons are mostly bouncing around, almost (but not quite) randomly. They kind of drift, as a group, in the direction of the current (actually, opposite the direction of the current, since electrons have negative charge).

When you think of the fact that the mass of an electron is approximately 0.5 MeV/c^2, that means that it would take about 500,000 Volts to get an electron to be moving in one direction at a relativistic speed. Normal voltages don't come close to that.

Answer 4

Not even close; in fact, they move quite slowly. The speed can be calculated by using the wire size, the amount of current, the size of the electric charge, and the number of metal atoms per unit volume. (Assume one charge per atom.)

Answer 5

No. It depends on the potential (voltage) and materials. All materials have a lower speed of light than the one we memorized (300,000 km/sec) and the more atoms the slower the speed.

Answer 6

Speed of Light.