Recent content by ijustlost

Well you need to find the minimum and maximum value of the band Energy - then W is the difference between them.. The easiest way is probably just by inspection.

Does anyone know of any practical uses for a type I superconductor, where it isn't possible to use a type II (which typically have higher critical temperatures so need less cooling etc)?

reilly - I understand how it comes from solving the equations, I was just wondering if there was a nice 'classical' picture, but I guess there isn't really one that isn't terribly inaccurate. jtbell - yeah makes sense

Remember that this time (5.19E-3) is the time that elapses in the pions rest frame, not the Earth's rest frame. In the Earths rest frame elapsed time will be longer. I don't think you can just assume the pions move at c. What you do know is the Total Kinetic of all the pions T = (Original...

A rod of length 2l is at rest in frame O' with co-ords (x',y',z')=(±l,λ,0) Observer O moves at speed u along the x axis. The first part of the question is just to derive the length contraction - fine, O measures the length as 2l / γ The next part has me stuck: "Show that, at t = 0...

Cheers, that makes sense. But why then may the first excited state have l=0,1 but not higher, the 2nd excited state have l=0,1,2 etc. I'm guessing the higher the energy the more the state may 'break' the symmetry of the potential. And also in a nuclear potential there isn't any such restriction...

Not quite an original paper, but Dirac's "Lectures on Quantum Mechanics" is worth reading

Why can't an electron in a coulomb field have an orbital angular momentum quantum number higher than it's principal quantum number (ie there is no 1p state etc.) I think is probably something I learned at one point, but I've forgotten and can't seem to find anything about it anywhere. I know...

What context was it used in? Might be clearer if you put down the whole equation / sentance it's used in..

Oops, stupid me! The answer is \frac{\pi}{cos(\frac{a\pi}{2})} I didn't work out the phase shift the function takes on along the top line of the path properly!

Ah thanks, I knew there was one somewhere!

P.s - is there a guide to using tex on physics forums somewhere? Then I could format the above properly!

I'm trying to find \int_{-\infty}^{\infty} \frac{exp(ax)}{cosh(x)} dx where 0<a<1 and x is taken to be real. I'm doing this by contour integration using a contour with corners +- R, +- R + i(pi), and I'm getting an imaginary answer which is \frac{2i\pi}{sin (a \pi)}. I'm thinking this is...

I think the only problem with the statement is the Amps bit. You're right that for there to be a potential difference you need a difference in charge, but if all the charge in the rod were at one end it could have a potential difference across it. Magnetic "voltage" is different to electric...

If there's only a tensile force acting, surely the shear stress is 0?