Resistance and Electric Potential

In summary, resistors reduce potential by creating an electric field that opposes the current. This happens even without a battery, as long as there is some resistance in the circuit.
  • #1
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This is probably a simple concept but I'm struggling a little bit understanding it. When power is dissipated through a resistor, how is potential actually lost? I understand energy is converted into heat and other forms, but isn't potential just defined as a function inversely proportional to distance and proportional to charge (i.e. q/r)? I'm sure I'm misinterpreting the different terms, though, because potential is at approximately the same level at all points on a conductor (assuming negligible resistance), so it can't simply be a function of distance.
 
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  • #2
Potential is a function of distance from charge, but each point in the conductor is roughly equally far apart from a similar amount of charges. This is what makes it a conductor. The charges in a conductor are free to move around. So if at one point there is higher potential than another, this will cause charges to move. They will move until they minimize their potential and at this point the potential will be uniform throughout the conductor. (the charges have naturally arranged themselves such that they are roughly equal distance from each other)
 
  • #3
ModusPwnd said:
Potential is a function of distance from charge, but each point in the conductor is roughly equally far apart from a similar amount of charges. This is what makes it a conductor. The charges in a conductor are free to move around. So if at one point there is higher potential than another, this will cause charges to move. They will move until they minimize their potential and at this point the potential will be uniform throughout the conductor. (the charges have naturally arranged themselves such that they are roughly equal distance from each other)

Oh I see. That makes a lot of sense. So if there was no resistor in a circuit, would the potential just keep building up?
 
  • #4
The current would build up. The battery or power supply is designed to put out a constant voltage, which is potential. So the potential across your entire circuit is constant.

For the situation with no resistor you should remember that nothing is a "perfect" conductor. The wire has a small amount of resistance. If you have no resistor in the circuit then you can't really neglect the wire's resistance, because that's all you have. With no resistor you have the minute resistance of the wire which leads to very large current (via ohm's law).
 
  • #5
ModusPwnd said:
The current would build up. The battery or power supply is designed to put out a constant voltage, which is potential. So the potential across your entire circuit is constant.

For the situation with no battery you should remember that nothing is a "perfect" conductor. The wire has a small amount of resistance. If you have no resistor in the circuit then you can't really neglect the wire's resistance, because that's all you have. With no resistor you have the minute resistance of the wire which leads to very large current (via ohm's law).

Okay. One last thing regarding this... How does this work regarding multiple resistors, for example two in a series? That is, what causes the change in potential between the terminals of an individual resistor, when the resistors themselves do not affect the charge distribution? I understand a battery creates an emf by moving particles, but what changes the potential within a circuit?
 
  • #6
Good question. I think resistors do affect the charge distribution. Or I should say, in a resistor the charges are not as free to move around. Because they don't move around as easily they can put up a local electric field that "resists" the current entering the resistor. Then you have a lower potential on the other side, since the other side is connected to the battery.

Im sure this can be explained better by someone more knowledgeable...
 
  • #7
ModusPwnd said:
Good question. I think resistors do affect the charge distribution. Or I should say, in a resistor the charges are not as free to move around. Because they don't move around as easily they can put up a local electric field that "resists" the current entering the resistor. Then you have a lower potential on the other side, since the other side is connected to the battery.

Im sure this can be explained better by someone more knowledgeable...

Okay thank you for your help.
 

1. What is resistance and how does it relate to electric potential?

Resistance is the opposition to the flow of electric current in a material. It is measured in ohms and is affected by factors such as the material's composition, length, and temperature. Resistance is directly related to electric potential, as an increase in potential difference (voltage) will result in an increase in current flow, and thus a decrease in resistance.

2. How does temperature affect resistance?

Temperature can have a significant impact on resistance. In general, as temperature increases, resistance increases as well. This is because as the temperature rises, the atoms and molecules in a material vibrate more, causing more collisions and hindering the flow of electrons.

3. What is the difference between series and parallel circuits in terms of resistance and electric potential?

In a series circuit, all components are connected in a single loop, with the same current flowing through each component. The total resistance of a series circuit is equal to the sum of the individual resistances. In contrast, a parallel circuit has multiple branches, with each component having its own path for current to flow. The total resistance of a parallel circuit is less than the individual resistances, and the voltage across each component is the same.

4. How does the length and thickness of a wire affect its resistance?

The longer and thinner a wire is, the higher its resistance will be. This is because a longer wire offers more obstacles for electrons to pass through, and a thinner wire has less space for electrons to flow. In contrast, a shorter and thicker wire will have a lower resistance, as there is less distance for electrons to travel and more space for them to flow.

5. How is resistance different in conductors and insulators?

In general, conductors have lower resistance compared to insulators. This is because conductors have a higher number of free electrons that can move easily, allowing for a greater flow of current. Insulators, on the other hand, have fewer free electrons and do not allow for the easy flow of current, resulting in higher resistance.

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