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Jul
18
accepted Applying Biot-Savart to a circular loop along central axis
Jul
18
comment Applying Biot-Savart to a circular loop along central axis
As for the symmetry argument, I'm visualizing B being perpendicular to the vector going from the circle to the point along the axis, as we keep changing this vector, we rotate it around in a circle, hence so does the vector B, but this is a circle in the y-z plane, hence B traces out a circle in the y-z plane and does not have a variable x component. Is that the kind of argument you were thinking of? I think it works! I come from math, and am not used to these kinds of non-rigorous arguments, but I'm growing quite fond of this kind of thinking.
Jul
17
comment Applying Biot-Savart to a circular loop along central axis
Yes I do agree! All I am saying is that for any ds where dB has 3 components, you can't use that simple trig to argue that the x-component is dB$\frac{R}{r}$. But, it has to be true if we are to sum over the circle. I'd like to see a picture showing how it still works when there are 3 components.
Jul
17
comment Applying Biot-Savart to a circular loop along central axis
The problem is that you can't say that the angle from the x axis to dB + the angle from dB to the y axis is 90 degrees and use the geometry of the big right triangle do compute the x component if there is a z component, so everything falls apart.
Jul
17
asked Applying Biot-Savart to a circular loop along central axis
Jun
23
comment potential difference across a bulb
Your .167 ohms is incorrect, so I unchecked you as the best answer.
Jun
23
comment potential difference across a bulb
@ Everybody, I don't understand why I was down voted. I sensibly phrased my question, and gave a very detailed (unfortunately wrong) answer to the question. Please, whoever down voted me, please explain so that I can improve next time I post a question. Thanks.
Jun
23
comment potential difference across a bulb
not sure if you read my message, but I said, I "won't" downvote you. I understand that you found another way to approximate the solution, which is not what I wanted, but because I recognize it's correct in its own way, I won't downvote you.
Jun
23
comment potential difference across a bulb
I won't downvote you, but if you read a clever solution below, you "DON'T" have to assume 120VAC, which is really what I've been wondering. Indeed there is a way to figure it out without that assumption which the author did not give to me since we really don't need it. You can set up two equations with two unknowns. See the comments in the answer below.
Jun
23
comment potential difference across a bulb
@AlfredCentauri It's the resistance that I'm struggling to see how to compute.
Jun
23
comment potential difference across a bulb
Let us continue this discussion in chat.
Jun
23
comment potential difference across a bulb
@K7PEH See my update above. I believe the author assumed we know that a bulb with 100W is meant at 120V which is standard in the US. Agree?
Jun
23
comment potential difference across a bulb
@K7PEH I still have to compute V_coord. To do so, I need to some over the whole circuit the resistances, you know how it works.
Jun
23
revised potential difference across a bulb
added 333 characters in body
Jun
23
comment potential difference across a bulb
It's impossible to compute that though because I don't know R_bulb.
Jun
23
comment potential difference across a bulb
I felt like my solution was wrong. Am I correct that the bulb and the cord are in series?
Jun
23
comment potential difference across a bulb
they should be in series. plus your equation isn't correct.
Jun
23
comment potential difference across a bulb
how do you know they are in parallel?
Jun
23
asked potential difference across a bulb
May
21
accepted Minkowski Diagram for Time-Like Separated Events