what makes this possible?
-how many of you have seen this before?
-how many of you the cause of this effect?
-meissner effect

introduction
-good morning blah blah
-explaining when it happens and what it means
-then move on to a bit of history and development
-meissner effect
-then tell a bit of applications
-not in deep

what superconductivity means?
-zero electrical resistance -> doesn't effect current
-happens when temperature reaches critical point
-normally there is resistance at 0K
-different materials have different critical temperatures
-temperatures are really low, around 20K and typically under -200C
-near absolute zero
-only happens on certain materials

timeline of materials
-dutch physicist found 1911, 4,2K, used helium
-nitrogen 77K, helium 4K
-until 1986 it was believed that Tc>30K not possible (LaBaCuO, lanthanum based)
-soon after that replaced lanthanum with yttrium->
-replaced liquid helium with nitrogen, significant jump
-easier to handle, cheap
-since 1993, highest Tc=135, ceramic material
-2008 iron-based family was found in japan

meissner effect?
-explain image
-superconductor is cooled below it's critical temperature
-when it is placed in magnetic field which is big enough the conductor magnetises
-characteristic for superconductors
-cool pics but real applications, too

applications
-power cables with low power loss (no resistance)
-superconducting magnets are the most powerful electronic magnets
*used in medicine (most used), mass spectrometers
*a lot lighter than equivelant magnets
*cern's large hadron collider
*fusion reactor ITER

conclusion
-that's all about it
-my point was to show you when it happens and what it means
-there was a brief introduction to timeline and meissner effect
-we also discussed on applications
-i hope you learned something from this
-thanks for attending the presentation
-you can ask questions now 

why does it drop suddenly?


Superconductors are also able to maintain a current with no applied voltage whatsoever,
a property exploited in superconducting electromagnets such as those found in MRI machines.
Experiments have demonstrated that currents in superconducting coils can persist for years without any measurable degradation.