I What is the net charge on the Earth?

[stefan r]

Suppose we have a flashlight that runs on alkaline batteries. We can take the flashlight inside of a Faraday cage. We can charge the cage to -1000 volts relative to a ground wire. The flashlight should work as normal. Electricity flows between the "positive" and "negative" terminals. Relative to the ground wire the battery's positive terminal would be at -998.5 volts.

...
it's actually more common for discharges from negatively charged areas of a storm cloud to a positively charged area of the earth
Dave

Saying that "lightning usually travels from a negatively charged cloud to a positively charged ground" can be a correct statement. That makes a tree similar to the positive terminal of a battery. The same tree would have a different charge if measured against the ionosphere or interplanetary space.

 

[PeterDonis]

Thread closed for moderation.

 

[PeterDonis]

Thread reopened. Some off topic posts have been deleted, and some off topic content has been removed from some other posts. Everyone please bear in mind that if you think another member's post violates the rules, you should report it, not start an argument about it in the thread.

 

[PeterDonis]

Thunder storms generate a net positive charge in their head, at the top, opposed by a net negative charge in the mid-lower part.
The bottom of the cloud is charged positive relative to the Earth's surface.

This seems a bit confusing. If thunderstorms generate net positive charge at the top and net negative charge lower down, wouldn't the bottom of the cloud be negatively charged?

 

[Baluncore]

This seems a bit confusing.

Think of capacitors in series. The plates are Earth surface, cloud base, top of cloud, ionosphere. |-+|-+|-+|

Back to the OP subject.
The ionosphere is a good conductor. It is a sphere with capacitance to the rest of outer space.
Charge distribution inside that outer conductive sphere are quite irrelevant to the external situation.
The Earth's conductive surface along with the atmosphere are on the inside, so not relevant to the external voltage.

 

[CWatters]

Just to confirm I was thinking about the Earth as a whole including the atmosphere.

However it occurs to me that I could ask the question about anybody that could absorb cosmic rays such as the recent visitor from outside the solar system. Before it became subject to the solar wind would it have built up a positive charge because most cosmic rays are positively charged?

 

[davenn]

This seems a bit confusing. If thunderstorms generate net positive charge at the top and net negative charge lower down, wouldn't the bottom of the cloud be negatively charged?

yes, this is correct, as stated in my references

from first paper

The rebounding droplets acquire a positive charge and are carried by the convective updraught towards the top of the cloud, while the hail pellets carrying a net negative charge fall towards cloud base.

page 9 of the second paper shows positive charge higher and negative charge lower in the storm

 

[PeterDonis]

Think of capacitors in series. The plates are Earth surface, cloud base, top of cloud, ionosphere. |-+|-+|-+|

But the same plate can't be both negatively and positively charged, at least not in an absolute sense. Are these charges relative? ("Relative" would mean, for example, that the cloud base is more positively charged than the Earth surface, but more negatively charged than the cloud top--but this by itself does not tell us whether any of these areas are negatively or positively charged in an absolute sense, i.e., excess or deficiency of electrons overall.)

 

[Baluncore]

However it occurs to me that I could ask the question about anybody that could absorb cosmic rays such as the recent visitor from outside the solar system.

What visitor would that be ?

Before it became subject to the solar wind would it have built up a positive charge because most cosmic rays are positively charged?

The cosmic rays reaching the Earth's surface may be mostly hydrogen nuclei, traveling fast and stripped of electrons. But we notice those energetic cosmic rays most because they have a significant mass relative to beta particles and there is a magnetic selection processes in their path to Earth.

Any body will sweep up slow electrons as well as being plastered with fast protons, we do not know the relative charge population statistics, or the capture cross-section, so we cannot be sure on which side of zero the net charge will fall. My assumption is that the electron gathering or repelling ability of a body traveling through outer space will be determined by it's present charge, so we can expect it to stabilise near neutral.

When examining the Earth–Ionosphere capacitor we see that the negative ground, relative to the positive ionosphere has a gradient that is self-regulating. That is evident because charges move in the atmosphere, as insulation it is on the edge of breakdown. Any change in potential gradient will change the circulating currents and so regulate the potential gradient.

The fact that the Earth's surface is negative relative to the ionosphere shows that the charge on the surface is not due to incident protons alone and that other more significant processes must be going on.

But the same plate can't be both negatively and positively charged, at least not in an absolute sense.

All things are relative. Three plates make two series capacitors. The middle conductive plate will form an equipotential. Some electrons on that plate will be attracted towards the surface on the more positive side, while being repelled away from the surface on the negative side, leaving some holes. So there will be a charge separation across that plate. That charge distribution is the displacement current that flowed when the capacitor was charged. Since the plate is a good conductor, (not a capacitor), there will be no voltage difference on the conductive middle plate.

Think of two electrolytic capacitors connected in series. Is the common terminal one or two conductors ?

 

[CWatters]

What visitor would that be ?

https://www.nasa.gov/feature/solar-system-s-first-interstellar-visitor-dazzles-scientists

The cosmic rays reaching the Earth's surface may be mostly hydrogen nuclei, traveling fast and stripped of electrons. But we notice those energetic cosmic rays most because they have a significant mass relative to beta particles and there is a magnetic selection processes in their path to Earth.

Any body will sweep up slow electrons as well as being plastered with fast protons, we do not know the relative charge population statistics, or the capture cross-section, so we cannot be sure on which side of zero the net charge will fall. My assumption is that the electron gathering or repelling ability of a body traveling through outer space will be determined by it's present charge, so we can expect it to stabilise near neutral.

When examining the Earth–Ionosphere capacitor we see that the negative ground, relative to the positive ionosphere has a gradient that is self-regulating. That is evident because charges move in the atmosphere, as insulation it is on the edge of breakdown. Any change in potential gradient will change the circulating currents and so regulate the potential gradient.

The fact that the Earth's surface is negative relative to the ionosphere shows that the charge on the surface is not due to incident protons alone and that other more significant processes must be going on.
All things are relative. Three plates make two series capacitors. The middle conductive plate will form an equipotential. Some electrons on that plate will be attracted towards the surface on the more positive side, while being repelled away from the surface on the negative side, leaving some holes. So there will be a charge separation across that plate. That charge distribution is the displacement current that flowed when the capacitor was charged. Since the plate is a good conductor, (not a capacitor), there will be no voltage difference on the conductive middle plate.

Think of two electrolytic capacitors connected in series. Is the common terminal one or two conductors ?

Thanks.

 

[JMz]

All things are relative.

No, equal numbers of protons and electrons (esp., un-ionized atoms) are neutral by definition. Some things (about charges) are indeed relative, but not all.

 

[Baluncore]

No, equal numbers of protons and electrons (esp., un-ionized atoms) are neutral by definition. Some things (about charges) are indeed relative, but not all.

When the number of protons is in a 1:1 ratio relative to the number of electrons, the net charge will average zero.
The populations are quite unrelated. Some of my relatives are pedants too, relatively speaking.

 

[JMz]

The net charge is defined by the difference, not the ratio. The OP asked about the net charge.