BCalculate Speed of Electrons/Current in Circuits - Sparky_B

In summary: The momentum you had when you started moving will carry you all the way to the next red light, but your kinetic energy (the energy of motion) will be dissipated in the process. Resistance is how you convert this energy into heat.
  • #1
Sparky_
227
5
Greetings,

I would think this question belongs in a "Electro-magnetics" section, if it is not relevant in this section please move it accordingly.

How can I calculate the velocity of the electrons or the current within a circuit?

Meaning, how can I show how resistance affects the speed of the current?

How can I show how various conductors affect the speed of individual electrons or current?

Likewise for various dielectrics?

Thanks
Sparky_
 
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  • #3
Sparky_ said:
How can I calculate the velocity of the electrons or the current within a circuit?

How can I show how various conductors affect the speed of individual electrons or current?

You might want to note that the speed of the current is not the same as the speed of the electrons.

The drift velocity of the electrons mentioned by Ben Niehoff is *snails pace*. It would take something like a year or so for a single electron to cover the distance from the plug to the household applicant, assuming it runs on DC. In an AC circuit the average drift velocity of the electrons are zero.

But the electric field that drives the electrons propagates through the wire at near speed of light, so *all* conduction electrons in the wire begins to move at nearly the same instant, and thus the speed of the current would be the speed of light in the appropriate medium.

Also, it doesn't really make sense to speak of electron speed or current speed in dielectrics, as a dielectric by definition is a insulator. Still, the electric field propagates with the speed of light in the given dielectric.
 
  • #4
why don't the electrons themselves travel , aren't they free to travel or are they only free to "roam" about their atoms ?

what does resistance do in the atomic level?

i hope sparky doesn't consider this as high jacking his thread...?!
 
  • #5
AhmedEzz said:
why don't the electrons themselves travel , aren't they free to travel or are they only free to "roam" about their atoms ?

what does resistance do in the atomic level?

THe electrons are free to move, but their motion is by far dominated by the random thermal fluctuations, but these average to zero, so it is net displacement of an electron when you apply the electric field that is referred to as the drift velocity

As for resistance, the electrons colide with the massive nuclei as the move through the wire, transfering their kinetic energy to thermal energy as they go. Picture it, if you like as you driving your car with constant acceleration, but being forced to stop at red light at every 50 meters
 

1. How do electrons move in a circuit?

Electrons move through a circuit due to an electric field, which is created by a difference in voltage between two points. This electric field causes a force on the electrons, causing them to move from the negative terminal (where there is an excess of electrons) to the positive terminal (where there is a deficiency of electrons).

2. What is the speed of electrons in a circuit?

The speed of electrons in a circuit can vary, but on average it is about 0.03 millimeters per second. This may seem slow, but keep in mind that there are billions of electrons moving simultaneously in a circuit, creating an overall flow of electricity.

3. How is current related to the speed of electrons?

Current is a measure of the rate at which charge (in this case, electrons) flows through a circuit. It is not directly related to the speed of individual electrons, but rather the overall flow of electrons. Current is measured in amperes, or amps, and is represented by the symbol "I".

4. Can the speed of electrons be changed?

Yes, the speed of electrons can be changed by altering the voltage or resistance in a circuit. Increasing the voltage will increase the speed of electrons, while increasing the resistance will decrease the speed. However, keep in mind that the speed of electrons is not the same as the current, which depends on the number of electrons flowing through a circuit.

5. How is the speed of electrons calculated?

The speed of electrons can be calculated using the formula: speed = current/electron density x cross-sectional area. The current can be measured in amps, electron density in electrons/m^3, and cross-sectional area in m^2. Keep in mind that this formula gives an average speed, as the actual speed of electrons can vary within a circuit.

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