# Search results

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
16. ### How do overhead projectors project black onto a screen?

if you projected light of 3 wavelengths: Red, green and blue. of all the same intensity then it equals white? what about if you projected 4 different wavelengths? you just added another one in? under what condition will it appear to be white?
17. ### Converging and diverging lens

any lens that is thicker in the middle than at the edges is a converging lens.
18. ### How do overhead projectors project black onto a screen?

that would be cool if you could project black. is there some kind of particle you could launch in a beam that would absorb all photons?
19. ### What creates the magnetic field on a cyclotron?

Thanks bob. Once I piece together all of this information I hope I can find the time to assemble some 3d Models in Maya for Educational purposes. I will probably start with modeling a linear accelerator though. I was just curious about cyclotrons because my grandfather worked on a Cyclotron at...
20. ### Visualizing 4-d

if time is a dimension then we see 4d all the time don't we? we live and breathe in 4d don't we?
21. ### What creates the magnetic field on a cyclotron?

wouldn't you have the particles spinning for quite a while? how are the particles accelerated? it seems to me that this does not explain what object accelerates these particles as they make laps. Also, on the accelerators like the LHC. Are quadrupoles the primary method for focusing the beam...
22. ### What creates the magnetic field on a cyclotron?

what creates the magnetic field on a cyclotron? in all of the schematics I am looking at it just says "magnetic field points up" like it is extremely apparent as to what creates the magnetic field. I was thinking that a bunch of small diameter solenoids packed side by side would be the best way...
23. ### Visualizing 4-d

the color defines the location on another axis for every point does it not?
24. ### Visualizing 4-d

You can also do it by animating a variable. like this https://www.youtube.com/watch?v=F3d07Xe4WPQ
25. ### Visualizing 4-d

how about color? we use color all the time for this. http://www.mediafire.com/file/xdtbyldidzy/4d.png [Broken]
26. ### Electromagnetic Field Detector

I would need it to work with wavelengths outside of the visible spectrum. I don't need it to tell me the wavelength, but I just need to know the intensity. I will read about bolometric thank you for the keyword.
27. ### Why long Wave is better?

oh yea, i did not think about that lambda=v/f VHF frequench = 30 MHz wavelength = 10 m longwave frequency = 30kHz wavelength = 10000m!!! 10km! that is huge. have any diffraction experiments been done with massive wavelengths like this?
28. ### Electromagnetic Field Detector

I am looking for an electromagnetic field detector that can detect use to detect the intensity of wave on a grid and return the results to a computer. the higher the resolution the better. does anyone know where this can be purchased? how could one be designed?
29. ### Why long Wave is better?

you could test this pretty easy right. just get a wall of concrete or something and a dipole. then set it to oscillate at various frequencies on one side of the wall. Then on the other you put a Electromagnetic Radiation Detector and compare the levels for different wavelengths. this would work...
30. ### Particle Accelerator Schematics

it would be great if someone could work with that photographer and get all of those 3D images annotated.