Jump to content
Bobabuilder

Adding voltage to a faraday cage

Recommended Posts

If you had a square faraday cage grounded at the bottom and wanted to "add 5000 volts" is only instruction I saw.   How would you go about that?

I only heard that 5000 volts were added to the exterior of the faraday cage.    What would be the simple and cheap ways to add 5000 volts to the exterior of a Faraday cage for fun or folly?

Share this post


Link to post
Share on other sites

Ask the genius who wrote that instructions on how to prevent the 5000V to go to ground in short circuit.  And you do not 'add' voltage, you apply voltage.

Share this post


Link to post
Share on other sites
41 minutes ago, Bobabuilder said:

If you had a square faraday cage grounded at the bottom and wanted to "add 5000 volts" is only instruction I saw.   How would you go about that?

First step: isolate it from ground.

Second step: buy a 5000V generator or voltage converter.

If you want more than 5000V, you could use a Van der Graaf generator: https://science.howstuffworks.com/transport/engines-equipment/vdg3.htm

Share this post


Link to post
Share on other sites
2 hours ago, Bobabuilder said:

If you had a square faraday cage grounded at the bottom and wanted to "add 5000 volts" is only instruction I saw.   How would you go about that?

I only heard that 5000 volts were added to the exterior of the faraday cage.    What would be the simple and cheap ways to add 5000 volts to the exterior of a Faraday cage for fun or folly?

As a Faraday cage only blocks changing fields, not constant voltage, what is the point?

Why not just apply the voltage to a wire or capacitor? That is, er, potentially just as lethal.

Share this post


Link to post
Share on other sites
1 hour ago, Carrock said:

As a Faraday cage only blocks changing fields, not constant voltage

Would you like another guess?

 

Share this post


Link to post
Share on other sites
22 minutes ago, John Cuthber said:

Would you like another guess?

 

No.

In the spirit of this site, do not provide the correct answer.

Share this post


Link to post
Share on other sites
1 minute ago, Carrock said:

No.

In the spirit of this site, do not provide the correct answer.

Is that why you made that incorrect assertion?

Share this post


Link to post
Share on other sites
8 minutes ago, Carrock said:

No.

In the spirit of this site, do not provide the correct answer.

7 minutes ago, John Cuthber said:

Is that why you made that incorrect assertion?

 

I should have known you'd take me literally.

Will you edit Wikipedia's incorrect assertions?

Share this post


Link to post
Share on other sites

Does wiki say this

a Faraday cage only blocks changing fields, not constant voltage

?

Share this post


Link to post
Share on other sites
29 minutes ago, Sensei said:

Buy? You can make 5000 V DC from 230/110V AC using series of rectifying diodes with capacitors:

I am assuming, from the fact they asked the question, that the OP doesn't have the knowledge, skills and resources to do that.

Share this post


Link to post
Share on other sites
1 hour ago, John Cuthber said:

Does wiki say this

a Faraday cage only blocks changing fields, not constant voltage

?

No.

Does wiki say this

a Faraday cage blocks changing fields, and constant voltage

?

No.

I'm not familiar with the concept of blocking/not blocking constant voltage in a conductor. I can live without this knowledge.

 

Does wiki say this?

Quote

Due to [electrostatic]  induction, the electrostatic potential (voltage) is constant at any point throughout a conductor.

Yes.

 

 

Fun/scary video. You can see the arcing at about 16s as the linesmen connect themselves and the helicopter to the live high voltage line.

As the linesmen are wearing Faraday cages and the frequency (60Hz) is too low for conditions inside the cages to differ much from D.C., I presume you claim the voltage inside their cages is pretty near zero.

Ask one of them to drop an insulated wire from inside her cage to you on the ground. Good luck persuading her.

Linesmen are so conservative and overcautious that not one living linesman has ever tried this experiment.

 

Three posts in this thread and you've provided no useful information. Why bother?

Share this post


Link to post
Share on other sites
13 hours ago, Carrock said:

a Faraday cage only blocks changing fields

Still wrong.

Share this post


Link to post
Share on other sites
3 hours ago, John Cuthber said:

Still wrong.

OK. I looked at a few of your posts and I finally get it.

Anyone who begins a sentence with

Quote

At the risk of seeming smug, have a look at my post-count and status as a resident expert...

is immune to criticism.

Share this post


Link to post
Share on other sites

No.

If I posted something like 

11 hours ago, John Cuthber said:

a Faraday cage only blocks changing fields

I'd still be criticised for being wrong.

 

20 hours ago, Carrock said:

No.

Does wiki say this

a Faraday cage blocks changing fields, and constant voltage

?

No.

I'm not familiar with the concept of blocking/not blocking constant voltage in a conductor. I can live without this knowledge.

 

Does wiki say this?

Yes.

 

 

Fun/scary video. You can see the arcing at about 16s as the linesmen connect themselves and the helicopter to the live high voltage line.

As the linesmen are wearing Faraday cages and the frequency (60Hz) is too low for conditions inside the cages to differ much from D.C., I presume you claim the voltage inside their cages is pretty near zero.

Ask one of them to drop an insulated wire from inside her cage to you on the ground. Good luck persuading her.

Linesmen are so conservative and overcautious that not one living linesman has ever tried this experiment.

 

Three posts in this thread and you've provided no useful information. Why bother?

OK, here is some information that may be useful to people working in conductive suits on high voltage systems.

Make sure that any holes in the suit are small.

The exact definition of "small" depends on context.

In the particular case of a hole with a wire running through it the value tends to zero.

Because, in the case of a "faraday cage" with a wire leading through a hole in it, you don't have a faraday cage.

 

 

 

 

Share this post


Link to post
Share on other sites

Okay.    Thanks all.

Van de graaff sounds fun and probably what I'm after.     It involved confusing the sense of direction in insects by blocking the earths magnetic field and such.
Pretty dry stuff.   

The results were something akin to lessened directional instincts within a faraday cage.   Returned directional instincts within a grounded faraday cage.   Above average directional ability when 5000 volts was added to the cage.   (Added/applied... I cannot recall what was written?).

Just trying to understand the mechanics of something I had read but that's not a physics  question.   I am not making any claims or promoting that thought.   I am just trying to grasp how he could have had a  5000v external energy without shorting everything.   I was ignoring static electricity.

Thanks all

Share this post


Link to post
Share on other sites
On 7/10/2019 at 12:40 PM, Carrock said:

As a Faraday cage only blocks changing fields, not constant voltage, what is the point?

A voltage is not a field, so there’s an issue with this, but saying that a faraday cage only blocks AC is wrong.

The field inside a conducting sphere depends only on the charge inside the sphere. Not the outside field. IOW, it blocks DC as well.

Googling on ‘field inside conductor’ should give you many options for confirmation and explanation.

Share this post


Link to post
Share on other sites

As all I had to go on with Cuthber was 'you are wrong' I attempted to concentrate on the thing I felt sure was correct, the inability of a Faraday cage to prevent an applied D.C. voltage from appearing on its inner conductive surfaces. The voltage etc of any insulated object in the cage is irrelevant.

Against John Cuthber any hint I might have made a mistake elsewhere (as I realised I had after my first post or two - I should have only mentioned voltage, not fields) would be a rhetorical blunder. The  Cuthber/Carrock/Swansont part of this thread is a rhetorical debate, not physics.

 

I'm not sure of the etiquette of quoting someone who changes the meaning when he quotes himself

19 hours ago, John Cuthber said:

Still wrong. a Faraday cage only blocks changing fields

so I'll leave this quote as John Cuthber wrote it save with the original struck out.

 

I was not surprised John Cuthber did not specifically say I was wrong on any of the issues you mentioned as I have learned his authority is such that his opinions are not open to challenge and I was not going to mention anything more about those issues.

 

 

1 hour ago, swansont said:

A voltage is not a field, so there’s an issue with this, but saying that a faraday cage only blocks AC is wrong.

The field inside a conducting sphere depends only on the charge inside the sphere. Not the outside field. IOW, it blocks DC as well.

Googling on ‘field inside conductor’ should give you many options for confirmation and explanation.

'A voltage is not a field, so there’s an issue with this'

Not the outside field. IOW, it blocks DC as well.'

 

So the OP should have asked about fields and currents, not voltage as there’s an issue with this./s

I note you twice mention current being blocked but not voltage. The clear implication is that John Cuthber is right with his deniable claim that e.g. constant voltage is blocked from the (conductive) inside of a Faraday cage.

 

'The field inside a conducting sphere depends only on the charge inside the sphere. Not the outside field. IOW, it blocks DC as well.'

A bit ambiguous. Anything non conductive inside the sphere blocks D.C.. If there's a constant voltage across the sphere I'd expect some direct current on the inner conductive surface of the sphere, dependent on the magnitude of the internal field. I don't see how the internal field would prevent such current flow.

 

 

Your (correct) selective facts are much more effective than Cuthber's empty rhetoric....

 

You can ignore my report of Cuthber's last post as it was clearly pointless.

 

My rhetorical skills are clearly inadequate for this forum so I'm taking an indefinite sabbatical.

+1 to Cuthber and you for his win.

 

 

Share this post


Link to post
Share on other sites
8 hours ago, Carrock said:

As all I had to go on with Cuthber was 'you are wrong' I attempted to concentrate on the thing I felt sure was correct, the inability of a Faraday cage to prevent an applied D.C. voltage from appearing on its inner conductive surfaces. The voltage etc of any insulated object in the cage is irrelevant.

It's really a binary situation, so if the answer is not "no" then it is "yes" (and vice-versa)

Quote

Against John Cuthber any hint I might have made a mistake elsewhere (as I realised I had after my first post or two - I should have only mentioned voltage, not fields) would be a rhetorical blunder. The  Cuthber/Carrock/Swansont part of this thread is a rhetorical debate, not physics.

I'm pretty sure the issue of the electric field inside a conductor is physics.

 

 

Share this post


Link to post
Share on other sites
14 hours ago, Carrock said:

I attempted to concentrate on the thing I felt sure was correct, the inability of a Faraday cage to prevent an applied D.C. voltage from appearing on its inner conductive surfaces.

If you are inside a conductor- like your power line workers- the pattern of voltages in the outside world can do as it pleases. None of them will affect you. They may induce currents in the suit when they change.

In particular, no DC arrangement of potentials fields, or voltages outside the conductor will affect you if you are inside it.

That's the sense in which a Faraday cage works just fine for DC and the sense in which the thing you're sure of is wrong.
You were simply mistaken. It would have been better if you had asked for help, but you went off on some daft tangent  about 

On 7/10/2019 at 7:53 PM, Carrock said:

No.

In the spirit of this site, do not provide the correct answer.



Now, what was that about rhetoric?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.