Charge accumulated at two ends of resistor/inductor?

Click For Summary

Discussion Overview

The discussion centers on the accumulation of charge at the ends of resistors and inductors within electrical circuits. Participants explore the presence of electric fields, potential differences, and the implications of these factors on charge distribution in both components. The inquiry includes theoretical considerations and practical detection methods for these charges.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions whether charges accumulate at the ends of resistors and inductors, suggesting that a conservative electric field and potential difference imply the need for charge accumulation.
  • Another participant asserts that surface charge density is distributed along the entire surface of the resistor or inductor wire, not just at the ends, to maintain the necessary electric field.
  • A follow-up inquiry seeks clarification on whether these accumulated charges can be detected by devices.
  • It is proposed that while accumulated charges are detectable with a voltmeter, they cannot be measured directly without detailed knowledge of the circuit's geometry and components, as well as solving Maxwell's equations for charge density.
  • A later reply references a lecture that discusses the buildup of charges and the establishment of a conservative electric field, indicating that some charges are always present to maintain the electric field.

Areas of Agreement / Disagreement

Participants express varying views on the nature and detectability of accumulated charges, with some agreeing on the presence of surface charge density while others raise questions about measurement and detection methods. The discussion remains unresolved regarding the specifics of charge detection and the implications of charge distribution.

Contextual Notes

Participants note the complexity of calculating charge density, which depends on multiple factors including circuit geometry, voltage, current sources, and the properties of the components involved. The discussion highlights the challenges in applying theoretical principles to practical measurements.

kelvin490
Gold Member
Messages
227
Reaction score
3
In a simple circuit are there any charges accumulated at two ends of resistor? There is an conservative and thus electrostatic electric field and potential difference across the resistor. It seems it is only possible if positive and negative charges are accumulated at two ends to provide the electric field. Can these kind of extra charges be detected in a real resistor? How?

Same questions for inductor in the case of changing current in inductors. Thank you.
 
Physics news on Phys.org
yes in both cases . To be more accurate there is surface charge density *distributed properly* along the whole surface of the resistor or the wire the inductor is made and not only at the edges. What i mean by *distributed properly* is that if for example the wire makes a curve, there has to be surface charges along the curve such as to provide the proper electric field for the electrons to follow the curved path.

As to why the charges are in the surface of the conductor (most of them) is something that follows if we apply maxwell's equations and ohm's law ##\vec{J}=\sigma\vec{E}## for the interior of any conductor with conductivity ##\sigma##. For details check post #7 in this thread https://www.physicsforums.com/threads/electric-field-inside-a-closed-conductor.812046/#post-5097477
 
Last edited:
  • Like
Likes   Reactions: kelvin490
Thanks for the answer. I would also like to ask are these accumulated charges detectable by some devices?
 
Detectable yes by a simple voltmeter, but not measurable.To calculate them one should know the exact geometry of the circuit, the voltage and current sources in it, all the resistances and inductances and capacitances in the circuit, and then solve the maxwell's equations for the charge density ##\rho## of the circuit. This is very hard thing to do, can be done only with the help of computer programs.

When we connect the voltmeter in two points along a resistor, it is the surface charges at those two points that redistribute again along the leads of the voltmeter and thus create an electric field and a current inside the voltmeter and so they make the voltmeter to operate.
 
Last edited:
  • Like
Likes   Reactions: kelvin490
Delta² said:
Detectable yes by a...

Thanks. There is a lectures explain it in terms of accumulated charges ( ). From 41:00 to 45:00 he explained that charges are build up and conservative field was set up. In 43:00 to 43:30 he said there are always some charges to keep the E field.
 
  • Like
Likes   Reactions: Delta2

Similar threads

  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 21 ·
Replies
21
Views
4K
Replies
36
Views
4K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 42 ·
2
Replies
42
Views
4K
  • · Replies 17 ·
Replies
17
Views
3K
  • · Replies 16 ·
Replies
16
Views
4K
  • · Replies 4 ·
Replies
4
Views
17K
  • · Replies 2 ·
Replies
2
Views
11K