# Recent content by tot

1. ### Fermi Level for Silicon

i dont understand the equation. please explain how you find the fermi level
2. ### Fermi Level for Silicon

is 1.12eV the width of the band gap or the fermi level? what is the fermi level for undoped silicon?
3. ### Fermi Level for Silicon

what I've been told there is two groups of energy levels called the valence and the conduction band. what is the fermi level for silicon? how wide is the band gap for silicon?
4. ### Efficiency of mag lev

doesn't a lot of power have to be used to run the electromagnets that lift the entire weight of the train? It seems that a maglev train would be highly inefficient, but very quiet, fast and smooth. Can somebody verify this? because in a train with wheels, the lift is provided by the contact of...
5. ### Medical I heard there is a disease where you don't sleep

:) Physics is a disorder where you don't sleep? or I mean order. it's orderly.
6. ### Kinetic energy in polar coordinates

http://web.me.com/dmwilliams/photo.jpg Here is the derivation.
7. ### Linear Algebra proof (nonsingular matrices)

is it just me or is the math department lame. Why do we need so many contradicting words for the same thing correct me if I am wrong "non-singular"="One single trival solution"= "invertible" "singular" = "many solutions" ="not invertible"
8. ### Helium Leak Detectors

from my experience I could not even notice any time. Perhaps my enclosures are small in comparison to yours. I would say perhaps 3 cubic meters on the inside of a 6 in pipe. Does it propagate faster because of the vacuum? Because it does not seem like the pumping would be making much of an air...
9. ### Is Anti-Gravity a myth?

I thought the conclusion was that we don't have a unified theory that unites gravity, Electromagnetic, and the strong and weak forces. All of the equations we have have problems. Doesn't this leave room for potentially having control of gravity in the future?
10. ### Is Anti-Gravity a myth?

I really find it hard to believe Gravity is unstoppable. It seems every force must propagate over some medium. We learned that electromagnetism is and now we know how to contort it. Can't we contort gravity? but perhaps I don't know enough relativity and I am saying something stupid.
11. ### Helium Leak Detectors

I am trying to figure out how Helium Leak Detectors work. If a leak detector is pumping on an enclosure that is at a low pressure, the detector will detect helium leaking into the system instantly as far as my human senses can tell. The helium will propagate 4 meters in a time so small I can't...
12. ### Physics and robotics supplies?

I might be able to stream video when I have a good 3G connection. If it is up higher it will get better 3G too.
13. ### Physics and robotics supplies?

do you know what kind of propellors, motors and batteries I should use and where I can get them?
14. ### Physics and robotics supplies?

I need propellers to provide lift. I am going to build this with accelerometers to level. I am going to mount my iPhone on it and fly around using the GPS and 3G.
15. ### Physics and robotics supplies?

Does anyone know where I can get physics and robotics supplies? Where can I buy quadrupoles? Lithium Ion batteries propellers good DC motors Motors that can go to specific degree measures and stop vandegraff generators solenoids propellars small computers built to be onboard devices