Understanding Potential Drop in Electric Circuits: Exploring Electron Behavior

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In summary: The electric field is altered by the presence of the second resistor, causing the electrons to distribute their energy evenly between the two resistors. This results in the potential drop over the first resistor being reduced to half of the original value. In summary, the presence of a second, identical resistor in a circuit causes the potential drop over each resistor to be equal to half of the initial value of the source of emf. This is due to the altered electric field caused by the second resistor, causing the electrons to distribute their energy evenly between the two resistors.
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broegger
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I have a somewhat simple question, that I for some reason can't figure out..

suppose you have a circuit with a source of emf (e.g. a battery).. if you put a single resistor in this circuit there is a potential drop equal in size to the emf (i neglect internal resistance in the source).. now, if you place a second, identical resistor in the circuit the potential drop over the first resistor will be exactly half of it's initial value (that is, 1/2*emf).. my question is: how does the electrons "know" only to put half their energy in the first resistor and save the other half for the second - how does they detect the presence of the new resistor?

I'm sure I should know this, but my book doesn't offer any explanation..
 
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  • #2
Originally posted by broegger
.. my question is: how does the electrons "know" only to put half their energy in the first resistor and save the other half for the second - how does they detect the presence of the new resistor?
All the electrons know about is the electric field that pulls them along. They don't "save" energy. Imagine gazillions of electrons being jerked along through the resistor by the electric field. Each electron doesn't get far before it smacks into a lattice molecule, thus transfering its energy to thermal energy of the resistor. But then the electron once again gets accelerated by the field... until it smacks into the lattice again. Etc.
 
  • #3
Thank you.. so the presence of the new resistor somehow alters the electric field, so that the dissipated energy in the first resistor drops to the value corresponding to 1/2*emf??
 
  • #4
Maybe another simpler way to visualize this is to think about the analogy of water flowing. If you dump a bucket of water out of a window, let say 100 meters above the ground, it falls easily to the ground .. SPLASH!

But, if you take that bucket of water to a height of 100 meters and pour it on a rocky slope, it takes some time to reach the ground, but it eventually does (ignoring evaportaiton of course).

So, if this rocky slope is in TWO portions, with a free fall between them, you have little trouble visualizing the water flowing through the first part .. falling freely to the second stage, and resuming its journey until it is all at the bottom.

All it KNOWS is the potential difference and the flwo dynamics result from that alone.

Regards
 
  • #5
Originally posted by broegger
...so the presence of the new resistor somehow alters the electric field, so that the dissipated energy in the first resistor drops to the value corresponding to 1/2*emf??
Right.
 

1. What is electricity?

Electricity is a form of energy that results from the flow of electric charge. It is responsible for powering most of the devices and appliances we use in our daily lives.

2. How does electricity flow?

Electricity flows through a conductive material, such as a wire, when there is a difference in electrical potential (voltage) between two points. This creates a flow of electrons from the higher potential to the lower potential, similar to water flowing down a hill.

3. What is the difference between AC and DC electricity?

AC (alternating current) electricity is the type of electricity that is supplied to our homes and businesses. It constantly changes direction and has a varying voltage. DC (direct current) electricity, on the other hand, flows in one direction and has a constant voltage. It is commonly used in batteries and electronic devices.

4. How is electricity generated?

Electricity can be generated in various ways, including the use of fossil fuels, nuclear power, and renewable sources such as wind and solar. These methods involve spinning turbines that are connected to generators, which convert mechanical energy into electrical energy.

5. What are the safety precautions when dealing with electricity?

Electricity can be dangerous and it is important to take precautions when working with it. Some safety tips include: always turning off the power before working on electrical outlets or appliances, using insulated tools, and avoiding contact with water when working with electricity. It is also important to have a basic understanding of electrical circuits and to never overload them with too much current.

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