What does this mean?
(\vec A\cdot\nabla)\vec B
I read somewhere that
(\vec A\cdot\nabla)\vec B=\vec A\cdot\nabla\vec B
but this must be nonsense since you can't take the gradient of a vector.
Thanks. So if curl B = 0 at some point basically means that there is no source of magnetic field there? And then if curl B = 0 everywhere, it means there is no magnetic field? I guess this is what maCrabo means.
I think a problem for me is that I have always been used say that if curl B =...
Well, the reason I'm asking this is because we recently did a problem in my class where we were supposed to show some vector identity, with the conditions that both
curl B = 0
and
div B = 0
The problem was really about the maths, but it was phrased as if the field were a magnetic...