Liquid helium (and other similar fluids) can "climb up" the walls of their containers. Who does the work in this case, and what kind of energy does it use? I'm sure we can't make a perpetuum mobile out of this, so I guess some kind of energy must somehow be expended to make the fluid "climb up" the wall.


Question: Is 2N9013 a good replacement for 2N3904
Answer: It is a little more powerful than the 2n3904. Most likely the current gain is less, and and maybe also the maximal voltages.

Depending on your application that may be OK, which is quite likely if it is not too demanding. The correct thing would for you to check the numbers in the data sheet.