1 Sep
2008
1 Sep
'08
7:08 a.m.
bfranchuk at jetnet.ab.ca wrote:
der Mouse wrote:
The final speed of an accelerated electron only depends on voltage, not
the distance. A quick calculation gives the final speed close to 2% of
the speed of light at 200 V acceleration. That means it travels 10 cm in
aproximately 30 ns. (not counting relativistic effects and putting mean
speed to 1% of c)
In all practical cases the real distance is much smaller than that,
tubes usually isn't so big, at least not in a digital circuit. The x-ray
tube I have is 50 cm, but that is a totally different story. :-)
/G?ran
That brings up something I've occasionally
wondered about: how fast do
electrons move in a vacuum tube? (I'm talking about the free-flight
path between cathode and plate.) In particular, what's the time delay
between emission from the cathode and reception by the plate? I
imagine it depends on the plate voltage; does that make enough of a
difference to care about? I don't remember enough of the constants to
figure out what sort of acceleration a gradient of, say, 200 V/cm
imparts to a free electron....
I think you need study a broken tube to find the distance
from the cathode first.