Do EMF Sources Combine Conservative and Non-Conservative Electric Fields?

Click For Summary

Discussion Overview

The discussion revolves around the nature of electric fields within an EMF source, particularly focusing on the coexistence of conservative and non-conservative electric fields. Participants explore the implications of internal resistors in EMF sources, especially in the context of coils, and how these concepts relate to voltage drops and field characteristics.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that an EMF source does not inherently contain an internal resistor, while others suggest that real EMF sources can be modeled with an equivalent circuit that includes a resistor.
  • There is a proposal that within a coil acting as an EMF source, a conservative electric field may exist due to the internal resistor, although this is contested.
  • One participant expresses confusion regarding the measurement of voltage drops across internal resistors, noting that they are equivalent components and may not yield expected results in practical scenarios.
  • Another participant questions whether a combination of conservative and non-conservative fields could exist, reflecting uncertainty about the implications of these fields in the context of potential drops.
  • A later reply introduces the idea that any vector field can be viewed as a combination of conservative and solenoidal (non-conservative) fields, referencing external sources for further exploration.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature of electric fields within EMF sources, with multiple competing views on the existence and implications of conservative and non-conservative fields. The discussion remains unresolved regarding the specifics of these interactions.

Contextual Notes

There are limitations in the discussion regarding the definitions of conservative and non-conservative fields, the assumptions about internal resistors, and the implications of voltage measurements in practical scenarios. These aspects remain open to interpretation and further clarification.

tonyjk
Messages
227
Reaction score
3
Hello,

We know that the electric field generated by a changing magnetic field is not conservative. But, for example let' say we have an EMF source that has an internal resistor, the voltage drop across the source is equal to EMF-rI where r is the internal resistance. My question is, inside the EMF source, we have non-conservative electric field but also do we have conservative electric field due to its internal resistor? Please if someone didn't understand the question tells me.

Thank you.
 
Physics news on Phys.org
Hi.
You have brought up two different issues. An emf source does not, by definition, have an internal resistor. A real source of emf, if it is located in a specific place, (often) has an equivalent circuit of a true emf in series with a series resistor. All the same rules apply to that resistor as the other resistors in the circuit.
The issue of the non-conservative field is a separate one, I think and this video deals with it quite well. He presents it in an entertaining way.
 
sophiecentaur said:
Hi.
You have brought up two different issues. An emf source does not, by definition, have an internal resistor. A real source of emf, if it is located in a specific place, (often) has an equivalent circuit of a true emf in series with a series resistor. All the same rules apply to that resistor as the other resistors in the circuit.
The issue of the non-conservative field is a separate one, I think and this video deals with it quite well. He presents it in an entertaining way.

Yes, Sorry I meant about an emf source having a non-conservative electric field plus an internal resistor like in a coil. we can say that inside the coil we have a conservative electric field due to its resistor?
 
tonyjk said:
Yes, Sorry I meant about an emf source having a non-conservative electric field plus an internal resistor like in a coil. we can say that inside the coil we have a conservative electric field due to its resistor?
Doesn't that video describe exactly the situation you describe (in effect)?
 
sophiecentaur said:
Doesn't that video describe exactly the situation you describe (in effect)?

Okay, you mentioned before that an internal resistor is like a normal resistor. So yes it describes the situation. Just I was confused about the internal resistor and the difference between normal one because physically the coil is one object that has ideal coil + resistor.
Thanks anyway
 
tonyjk said:
an internal resistor is like a normal resistor.
But with one difference. You can't measure the voltage drop across it - and it's only an 'equivalent' component in as far as the loss mechanism can be anywhere and anything that's 'inside' the component. In your though experiment, you couldn't put a meter where the one in the video appears so you wouldn't get any paradoxical results. This stuff is quite confusing because of the temptation to assume that you really would get different results just by re-connecting a meter.
tonyjk said:
a conservative electric field due to its resistor
I'm not sure about this one because the resistor in question is distributed within the coil. Would the conservative field idea still apply?
 
sophiecentaur said:
But with one difference. You can't measure the voltage drop across it - and it's only an 'equivalent' component in as far as the loss mechanism can be anywhere and anything that's 'inside' the component. In your though experiment, you couldn't put a meter where the one in the video appears so you wouldn't get any paradoxical results. This stuff is quite confusing because of the temptation to assume that you really would get different results just by re-connecting a meter.

I'm not sure about this one because the resistor in question is distributed within the coil. Would the conservative field idea still apply?

Then why there's drop in potential if there's no conservative electric field?
 
tonyjk said:
Then why there's drop in potential if there's no conservative electric field?

Could there not be a combination of conservative and non-conservative field, perhaps?
 
Perhaps someone else could chime in, here?
 
  • Like
Likes   Reactions: tonyjk
  • #10
Having read around, I now find (why has it taken me so long?) that any vector field will be a combination of a conservative field and a solenoidal (non-conservative) field. Wikkers is a way into this. It makes good enough sense, when you think about it.
 
  • Like
Likes   Reactions: tonyjk

Similar threads

Undergrad Motional EMF in Faraday disc, co-rotating magnet axial mean flux
  • · Replies 5 ·
Replies
5
Views
1K
High School Troubleshooting Battery Internal Resistance Measurements
  • · Replies 105 ·
4
Replies
105
Views
13K
Graduate Electric field within a battery
  • · Replies 51 ·
2
Replies
51
Views
10K
Undergrad Is internal battery "emf" a conservative force?
  • · Replies 3 ·
Replies
3
Views
3K
Graduate Faraday's Law & Motional EMF Confusion
  • · Replies 3 ·
Replies
3
Views
3K
Undergrad Do electromagnetic fields have momentum?
  • · Replies 15 ·
Replies
15
Views
2K
High School Experiment issues (electromagnetism)
  • · Replies 42 ·
2
Replies
42
Views
4K
Undergrad Voltage drop in the internal resistance of a voltage source
  • · Replies 9 ·
Replies
9
Views
4K
Graduate Electric Fields with Motional EMF
  • · Replies 20 ·
Replies
20
Views
2K
Graduate Charge distribution in a resistor with a current
  • · Replies 4 ·
Replies
4
Views
17K