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seen Jul 18 at 18:21

Feb
22
comment Electric field caused by magnetic field
$\nabla$ is the gradient operator, not to be confused with $\Delta$.
Feb
22
comment Electric field caused by magnetic field
The electric field produced by a changing magnetic field is non-conservative. A conservative field is a field which can be written as the gradient of a potential function. In the case of the electric field produced by static charges, it can be written as $\mathbf{E}=-\nabla\phi$ where $\phi$ is the electric potential. When changing magnetic fields are introduced, it becomes $\mathbf{E}=-\nabla\phi-\partial \mathbf{A}/\partial t$ where $\mathbf{A}$ is the magnetic vector potential. Thus, it is no longer conservative.
Feb
22
answered Is light affect by gravity? Why?
Feb
22
comment Does gravitational force attract bodies with mass or with energy?
I wouldn't say it's "wrong." I'd say it's an approximation, and a very good one at that.
Feb
22
comment Does gravitational force attract bodies with mass or with energy?
Within the context of Newtonian gravity, yes, all you need to worry about is mass. Your textbook is correct.
Feb
22
answered Does gravitational force attract bodies with mass or with energy?
Feb
22
comment Null geodesic given metric
I mean the second-order differential equation, which is called the "geodesic equation."
Feb
21
comment I don't understand the relationship between electron indistinguishability and the Pauli exclusion principle
I'm not sure why I was down-voted. This is pretty much straight out of Griffiths'.
Feb
21
answered I don't understand the relationship between electron indistinguishability and the Pauli exclusion principle
Feb
21
comment Covariant derivative
In GR the connection is assumed to be torsion-free, so the Levi-Civita connection is all that is discussed in most introductory texbooks. Other connections are possible though, and the covariant derivative depends on the type of connection. If you're just learning GR then you don't really need to worry about any of that though.
Feb
21
answered Covariant derivative
Feb
21
answered Null geodesic given metric
Feb
21
answered Lagrange-Euler equations for a bead moving on a ring
Feb
21
awarded  Commentator
Feb
21
comment Electric field caused by magnetic field
The way E fields are generated is given to us by Maxwell's equations, and the equation for finding the E field produced by a charge and the equation for finding the E field produced by a changing B field are different.
Feb
21
answered Conservative Force and $1/r^2$
Feb
21
comment Electric field caused by magnetic field
No. The electric field around the solenoid looks similar to the magnetic field around straight current. I.e. it looks similar to the field in: school-for-champions.com/science/images/… .
Feb
21
answered Electric field caused by magnetic field
Feb
19
comment What are the biggest unanswered questions in physics today?
@hkBattousai I didn't know medical doctors used quantum mechanics :P.
Feb
17
comment Why is $\langle \partial_{\mu} f(x) \rangle=0$?
I don't own the books so I can't really determine the context. Could it have to do with the fact that the average amplitude of a sinusoidal wave is zero?