# The Basic of Electric Circuit

Discussion in 'Physics' started by anthonylauly, Jan 8, 2017.

1. ### #12 Expert

Nov 30, 2010
17,541
8,504
We did that in Chemistry 101.
That does not suggest that I'm a, "deep thinker".
I'm so shallow that I can't understand how it helps the TS to run off into things that call a college degree into question.
Guys. please. Try not to scramble the kid's brains while you tete-a-tete.

2. ### paul510 New Member

Mar 11, 2017
6
1

This is an electronics engineer's point of view. A physicist does not need to invoke the Ohm's law to define a potential difference between two points of space which is just the integral of the electric field through any path between these two points, and the electric field can exist in vacuum where no current can flow.

3. ### paul510 New Member

Mar 11, 2017
6
1
And I forgot to add: the voltage is equal to potential difference only for static fields, for time varying fields they are not the same! Consider a generator where a voltage is induced in a wire loop by varying the magnetic field flux : obviously this induced voltage cannot be obtained by subtracting potentials (then in the integral defining the potential difference we have to add the time derivative of the magnetic vector potential)

4. ### WBahn Moderator

Mar 31, 2012
19,295
5,234
The issue isn't static versus time-varying electric fields. It is conservative versus non-conservative electric fields.

5. ### WBahn Moderator

Mar 31, 2012
19,295
5,234
Larger problems have already been pointed out with the quoted claim. A capacitor most definitely can have a voltage across it without having any current flowing in it. An inductor most definitely can have a current flowing in it without having any voltage across is. Ohm's Law tells us only about the relationship between voltage and current in ohmic materials.

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6. ### paul510 New Member

Mar 11, 2017
6
1
Of course, for general fields it is conservative versus non-conservative issue, but this was an electronics question : here it is the same as static versus time-varying electric fields issue because a static electric field is always irrotational therefore conservative.

7. ### WBahn Moderator

Mar 31, 2012
19,295
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So you are saying that time-varying electric fields cannot be conservative?

8. ### paul510 New Member

Mar 11, 2017
6
1
May be in a configuration where the magnetic field induced by the varying electric field does not contribute to the magnetic flux across the circuit - I don't know if such configuration can exist, interesting question.

In the meantime I found this lecture giving some interesting examples for time-varying fields:
http://inds11.uni-klu.ac.at/lectures/The difference between voltage and potential difference.pdf

9. ### profbuxton Member

Feb 21, 2014
292
101
Oh for goodness sake! talk about going off in tangents. The OP only asked about voltage and potential difference and you all launch in almost a metaphysical discussion about stuff that most likely is over his head and doesn't clarify the situation at all! Keep it simple for learners!

ErnieM likes this.