# Question about the physics of mass spectrometry

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#1
If the positive ions are 'beamed' across a vacuum by high electric potential, then consider this: V=IR, so for there to be electric potential, there must be resistance in the vacuum. CAN SOMEONE EXPLAIN HOW THERE IS RESISTANCE IN THE VACUUM
0
1 year ago
#2
V=IR relates only to Ohmic conductors, in which, as is shown in the equation, p.d. and current are directly proportional. It can't be applied in all cases of electric current.

[EDIT] After a bit of research, it appears that vacuums actually have something called impedance rather than resistance. The impedance of free space is roughly 377 Ohms, but I'm not sure if this relates to mass spectroscopy. Vacuums are also rarely perfect and still contain a small amount of particles, producing a small amount of resistance.
Last edited by ProperLad; 1 year ago
0
1 year ago
#3
Maybe because it’s a human “made” vacuum - it doesn’t have perfect conditions that allow your calculations to cancel the resistance from the equation 🤷🏽*♀️
1
1 year ago
#4
(Original post by oliver3450)
If the positive ions are 'beamed' across a vacuum by high electric potential, then consider this: V=IR, so for there to be electric potential, there must be resistance in the vacuum. CAN SOMEONE EXPLAIN HOW THERE IS RESISTANCE IN THE VACUUM
It's vacuum with ions added to it

The ions carry a charge and are free to move through the 'vacuum'*... they are free charge cariers

*not really a vacuum because it has things in it - the things are those ions

if you stop putting charge carriers into a vacuum, vacuum is a good insulator
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