- #1
Shaun
- 3
- 0
What would happen if you took a battery into space? Would a current flow between terminals being it's in the vacuum of space?
Battery in Space? Current Flow in Vacuum?
Click For Summary
Discussion Overview
The discussion explores the behavior of a battery in space, specifically whether a current would flow between its terminals in a vacuum. Participants consider the implications of air as an insulator and the nature of resistance in a vacuum, as well as the effects of thermal electron emission.
Discussion Character
- Exploratory, Technical explanation, Debate/contested
Main Points Raised
- Some participants propose that no current would flow between battery terminals in Earth's atmosphere due to air acting as an insulator unless the voltage is high enough to ionize the air.
- Others argue that in a vacuum, the absence of air would suggest an even better insulating condition, potentially preventing current flow due to a lack of a conductive path.
- One participant questions the assertion that there is no resistance in space, prompting a discussion about the nature of resistance and its dependence on environmental conditions.
- Another participant introduces Paschen's Law, noting that breakdown voltage decreases with lower gas pressure but undergoes a significant change at very low pressures.
- Vacuum capacitors are mentioned as effective insulators in high voltage applications, suggesting that a vacuum can be beneficial in certain electrical contexts.
- A later reply raises the question of thermal electron emission and whether heating the battery terminals could facilitate current flow in a vacuum, despite the notion of infinite resistance.
- Historical context is provided regarding thermionic emission, with references to old valve radios and how electrons can cross a vacuum gap when attracted by a positive charge.
Areas of Agreement / Disagreement
Participants express differing views on whether a current can flow in a vacuum, with no consensus reached on the implications of thermal electron emission or the nature of resistance in space.
Contextual Notes
The discussion includes references to specific physical laws and concepts, such as Paschen's Law and thermionic emission, which may require further clarification or exploration of assumptions regarding vacuum conditions and electrical behavior.
- #2
davenn
Science Advisor
Gold Member
- 9,725
- 11,821
Hi Shaun
welcome to PF
what do you think would happen and why ?
does it flow between terminals in the Earth's atmosphere ?
Dave
welcome to PF
what do you think would happen and why ?
does it flow between terminals in the Earth's atmosphere ?
Dave
- #3
Shaun
- 3
- 0
Thank you :) I'm glad to be here. We'll I think on Earth no current would flow because air is some what of an insulator unless the voltage was high enough to Ionise the air "breakdown voltage" but in space there is no resistance and a potential always exists so I think it would flow :)
- #4
davenn
Science Advisor
Gold Member
- 9,725
- 11,821
think about what you said about the air and the ionisation
if air is (as you say) somewhat of an insulator ...
Don't you think a vacuum ... the absence of air, would be an even better insulator ?
There isn't anything between the terminals that can be ionised, so therefore, no conductive path can form
how's that sound to you ?
cheers
Dave
if air is (as you say) somewhat of an insulator ...
Don't you think a vacuum ... the absence of air, would be an even better insulator ?
There isn't anything between the terminals that can be ionised, so therefore, no conductive path can form
how's that sound to you ?
cheers
Dave
- #5
- 19,385
- 15,617
Shaun said:
Why do you think this? What IS resistance in your mind?
- #6
B0b-A
- 155
- 32
The breakdown-voltage does drop as the gas pressure is lowered ,
but undergoes a steep U-turn at about 1/100th of an atmosphere ...
http://en.wikipedia.org/wiki/Paschen's_law
The vacuum of space is less than a trillionth of Earth's atmospheric pressure.
but undergoes a steep U-turn at about 1/100th of an atmosphere ...
http://en.wikipedia.org/wiki/Paschen's_law
The vacuum of space is less than a trillionth of Earth's atmospheric pressure.
Last edited:
- #7
sophiecentaur
Science Advisor
Homework Helper
- 30,406
- 7,473
Vacuum capacitors are used in situations with very high voltages- such as in high power transmitters. A vacuum works very well for insulating capacitor plates, separated by a couple of cm. It's particularly useful because of the presence of high power RF fields which would involve losses in solid dielectric.
- #8
Shaun
- 3
- 0
Thanks for the replies everyone :) I was unaware of Paschen's Law, what if I heated up the terminal? Would that make a difference? Would thermal electron emission still take place in the vacuum of space and if so, how if space has infinite resistance?
- #9
davenn
Science Advisor
Gold Member
- 9,725
- 11,821
Hi Shaun
good to see you logging back in
One example of useful Thermionic emission is in the old valve radios ( valves, sometimes called tubes)
I don't know how old you are or if you know what valves are ?'
Usually a sealed glass tube with a vacuum inside
the most basic valve is a diode usually used as a rectifier for converting AC voltage to DC voltage
it has a cathode that when a voltage is supplied to it, it heats up and emits electrons. The other part is called an anode that has a positive voltage potential on it ...
Have a look at this diagram and see if you have any questions
electrons that are emitted from the cathode don't need a medium ( say a wire) to travel through.
The will happily cross the vacuum gap being attracted by the high voltage positive charge on the anode
cheers
Dave
good to see you logging back in
One example of useful Thermionic emission is in the old valve radios ( valves, sometimes called tubes)
I don't know how old you are or if you know what valves are ?'
Usually a sealed glass tube with a vacuum inside
the most basic valve is a diode usually used as a rectifier for converting AC voltage to DC voltage
it has a cathode that when a voltage is supplied to it, it heats up and emits electrons. The other part is called an anode that has a positive voltage potential on it ...
Have a look at this diagram and see if you have any questions
electrons that are emitted from the cathode don't need a medium ( say a wire) to travel through.
The will happily cross the vacuum gap being attracted by the high voltage positive charge on the anode
cheers
Dave
Attachments
Similar threads
High School
What Medium Does Light Travel Through in Space?
- · Replies 3 ·
- · Replies 29 ·
High School
Question about things moving through outer space
- · Replies 27 ·
High School
Dark Energy: Are We All Missing The Obvious?
- · Replies 4 ·
- · Replies 31 ·
- · Replies 58 ·