Is it really true that "no charge builds up" in a circuit?

In summary, the conversation discusses a circuit shaped as a rectangle with two long parallel wires connected by a battery and resistor. The question is whether the wires will attract or repel if the resistance is large enough. It is determined that they will repel due to the electrostatic force being stronger than the magnetic force. The concept of potential within a circuit is also brought up, and it is concluded that there can be different charge densities in different parts of the system.
  • #1
confundido
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This is a question we were asked quite some time ago:

Consider a circuit shaped as a rectangle, with two very long straight wires (parallel to one another), connected on one end by a battery and on the other end by a resistor.

We were asked to show--and this is not difficult--that if the resistance is large enough, the wires will attract rather than repel. (Due to the electrostatic force being stronger, in this case, than the magnetic force). In order for that to work out the wires have to actually be charged, not neutral. Is that the case? What is going on here? It has lead me to re-think my understanding of potential within a circuit altogether. I had previously thought of it as there being the same amount of charge on each side of the wire, but with each charge having V/q less energy of whatever type than the electrons on the other. I now think that is wrong. (Is it?)

Thank you for your help!
 
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  • #2
if the resistance is large enough, the wires will repel rather than attract. (Due to the electrostatic force being stronger, in this case, than the magnetic force).
A very large resister could be a break in the wire - then the two (real) wires are basically a capacitor. One wire would end up negative and the other positive.
Wouldn't the two wires attract then?

If the two wires are parallel, but the current is running in opposite directions, then wouldn't the magnetic force between them be repulsive?

I'm a little slow lately...
 
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  • #3
"No charge builds up in a circuit" can be worded more precisely as "the charge density at all points in the circuit is independent of time". It's true only if the system is static and has been allowed to settle down into a steady state, and it does not preclude different charge densities in different parts of the system (consider, for example, any system with non-zero capacitance somewhere).
 

1. What does "no charge builds up" in a circuit mean?

It means that the amount of electric charge entering a specific point in a circuit is equal to the amount of charge leaving that point. In other words, the total charge within the circuit remains constant.

2. Why is it important for no charge to build up in a circuit?

If charge were to build up in a circuit, it would eventually reach a point where the flow of electricity would stop. This would result in a malfunction or failure of the circuit.

3. Is it possible for charge to build up in a circuit?

In theory, it is possible for charge to build up in a circuit if there is a break or disruption in the flow of electricity. However, most circuits are designed to prevent this from happening.

4. How does the flow of electricity prevent charge from building up in a circuit?

The flow of electricity is maintained through the use of conductors, such as wires, which allow the movement of charged particles. Additionally, most circuits have components, such as resistors, capacitors, and diodes, that help regulate the flow of charge and prevent build-up.

5. Are there any circumstances where charge can build up in a circuit?

Yes, there are certain conditions where charge can build up in a circuit, such as when there is a malfunction or if the circuit is not designed properly. This is why it is important to follow proper circuit design principles and regularly check for any faults or malfunctions.

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