Timeline for Why is current a scalar quantity?
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17 events
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| Jan 7 at 18:38 | comment | added | Daniel Davee | It seems most people are confused by this. It's a vector for sure. The addition seems like it's a scalar addition only because the wires are 1 dimensional. Maxwell equations are explicitly vector equations. But we hardly ever think about current in higher dimensions. So consider water flow instead. In a river flow also adds like a scalar, but on a flood plane or in the ocean, it behaves like a vector. Attach a circuit to a sphere, anode on one side cathode on the other. On the surface of the sphere, the current would look like a vector field that obeys Gauss's law and the hairy ball theorem. | |
| Sep 10, 2020 at 17:48 | comment | added | Zo the Relativist | @Aron the 4-current in special relativity is current density, not current. The two things are different, related, concepts. Current density is a vector, current is a scalar, defined by $I = \int d{\vec A}\cdot {\vec j}$, where I is the current, and $\vec j$ is the current density, and $A$, is, say, the cross section of the wire in question. | |
| Sep 10, 2020 at 17:48 | comment | added | Zo the Relativist | Current density is a vector, $\rho {\vec v}$, and is the fundamental quantity. Current is a surface integral of this quantity that tells you how much net charge is crossing a boundary. Since a surface integral has a dot product in it, it is a scalar and invariant under rotations, since the rotation will act on both the velocity and the surface. | |
| Oct 15, 2017 at 13:27 | history | edited | AccidentalFourierTransform | CC BY-SA 3.0 |
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| Mar 21, 2017 at 20:10 | comment | added | Shashaank | @Ruslan Griffith clearly says again n again the current is actually a vector. It is clear that current is vector if one talks of surface currents . Only reason the author ignore vector nature of current in wire is because j is constant throughout. But actually current is a perfect vector. Griffith says this at 2 places. Why then he say this ? Is he wrong or the answers here wrong. If you want I can also tell you the pages where Griffith says all this or can post a picture ! Actually this is for all the answers here but I tag you since you are saying a bit against I being a scalar I.e with GRT | |
| Feb 4, 2015 at 16:24 | comment | added | R004 | Wikipedia talks about a four dimensional analog of 'electric current density'( a vector quantity well known to us in our three dimensions ). I'm talking about electric current. I hope it is clear. | |
| Jan 29, 2015 at 6:48 | comment | added | Aron | I can't help but notice that Relativity disagrees with you en.wikipedia.org/wiki/Four-current | |
| Jan 26, 2015 at 5:40 | history | edited | R004 | CC BY-SA 3.0 |
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| Oct 30, 2014 at 18:02 | comment | added | Ruslan | In fact, it may appear scalar, depending how you define differential cross-section vector $d\vec A$ in definition of current $I=\int\vec Jd\vec A$. If you define it so that it changes direction under parity inversion, then $I$ is pseudoscalar. Otherwise, it's scalar. Or I may be wrong, and $d\vec A$ has some unambiguous definition. | |
| Oct 30, 2014 at 17:06 | comment | added | R004 | Could you throw some light on current being a physical quantity other than a vector? | |
| Oct 30, 2014 at 16:15 | comment | added | Ruslan | Scalar quantity is a quantity, which is invariant under rotations. Current is not invariant under rotations. Also, the physical quantities can include pseudotensors (including pseudoscalars), and even things like sum of tensor and pseudotensor - such quantities are definitely not among those you listed. | |
| Oct 30, 2014 at 9:14 | comment | added | Ruslan | If a quantity is not a vector, this doesn't make it scalar. | |
| Jul 11, 2014 at 18:08 | history | made wiki | Post Made Community Wiki by R004 | ||
| Jul 9, 2014 at 16:42 | history | edited | R004 | CC BY-SA 3.0 |
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| Jul 9, 2014 at 16:35 | history | edited | R004 | CC BY-SA 3.0 |
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| Jul 9, 2014 at 16:27 | history | edited | R004 | CC BY-SA 3.0 |
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| Jul 9, 2014 at 16:01 | history | answered | R004 | CC BY-SA 3.0 |