Using ebook readers on aeroplanes?

[Shaggy]

Originally Posted by HarryT

It has nothing at all to do with grounding.

I believe it also has nothing at all to do with protecting against an internal electrical field.

Obviously, the answer is that if a passenger wants to use their cell phone during takeoff/landing, they just need to step outside.

[ThomasMc]

Originally Posted by jbjb

I'm afraid that's not right. A Faraday cage works because the charge on a hollow conductor distributes itself around the outside of that conductor in such a way as to result in no net electric field within the conductor. No ground connection is required for this.

/JB

If that were the case, then why do pilots fly hundreds of miles out of their path to avoid electrical storms, and why do planes have dissipators, to eliminate the buildup of charges that might attract lightening? It is these two things that prevent lightening strike related crashes, not a Faraday effect.

[ThomasMc]

Originally Posted by HarryT

Absolutely right. As Wiki succinctly expresses it:
It has nothing at all to do with grounding.

Harry, you "conveniently" neglected to quote the very next paragraph in that Wiki definition. Not that I'm surprised that you would do such a thing. Tsk tsk.

"If the cage is grounded, the excess charges will go to the ground instead of the outer face, so the inner face and the inner charge will cancel each other out and the rest of the cage would remain neutral."

[HarryT]

Originally Posted by Shaggy

I believe it also has nothing at all to do with protecting against an internal electrical field.

That's correct. The reference was made in answer to a point about lightning strikes.

Obviously, the answer is that if a passenger wants to use their cell phone during takeoff/landing, they just need to step outside.

That's obviously the answer, yes .

[HarryT]

Originally Posted by ThomasMc

Harry, you "conveniently" neglected to quote the very next paragraph in that Wiki definition. Not that I'm surprised that you would do such a thing. Tsk tsk.

"If the cage is grounded, the excess charges will go to the ground instead of the outer face, so the inner face and the inner charge will cancel each other out and the rest of the cage would remain neutral."

I didn't quote that because it's entirely irrelevent to the discussion at hand, which is what happens to aircraft when they are struck by lightning. An aircraft at 30,000ft is rather self evidently not grounded .

[Shaggy]

Originally Posted by HarryT

That's correct. The reference was made in answer to a point about lightning strikes.

Yep, I saw that. Just wanted to point out that protecting against lightening strikes has absolutely nothing to do with protecting against electronic devices inside the plane. It seemed like some others didn't understand that there is a difference.

[ThomasMc]

Originally Posted by HarryT

I didn't quote that because it's entirely irrelevent to the discussion at hand, which is what happens to aircraft when they are struck by lightning. An aircraft at 30,000ft is rather self evidently not grounded .

No, you originally brought it up in reference to radio signals, not lightening. You used lightening to back up your point. If that were true, as you claimed, about the Faraday effect cancelling them out, then it would also be true on the ground, and you would not be able to use your phone inside the fuselage there, either. In actuality, you can barely hear yourself think while taxing to the terminal, as everybody and their cousin is on their cell phone calling people to announce their arrival.

-> If your Faraday cage isn't grounded, then it merely becomes an antenna for your radio. <-

Harry, you are the most argumentative person on these forums. You argue even with the people who agree with you. It seems to be your only mode of communication. Chill.

[HarryT]

Originally Posted by ThomasMc

No, you originally brought it up in reference to radio signals, not lightening. You used lightening to back up your point.

I'm very sorry, but you're misrepresenting me. I made the point about Faraday cages in post #29, in reply to a point that "lightning strikes are more powerful than mobile phones". You then asserted in post #189 that Faraday cages only work if they are grounded, which is simply untrue. There is zero electric field inside a hollow conductor as a result of an external electric charge regardless of whether or not it's grounded. All that grounding does is to provide a mechanism for draining away that charge. On an aircraft, as you pointed out yourself, that's done by charge dissipators - basically spikes - which are often located on the trailing edge of the wing.

If that were true, as you claimed, about the Faraday effect cancelling them out, then it would also be true on the ground, and you would not be able to use your phone inside the fuselage there, either.

That would be true if planes were entirely sealed conductors. They aren't - they have windows, which radio waves can pass through. That's why you can use your mobile phone on a plane. If you were sitting inside a sealed metal box, your mobile phone wouldn't work.

[ThomasMc]

It has nothing to do with windows, Harry. An ungrounded Faraday cage is an antenna. Put a radio next to a metal window screen, and you'll get better reception. That was a trick I learned in the 70s, with my short wave radio. It isn't because the radio waves are passing through the little holes, they are smaller than the wavelength of the signal. Ground that screen, and you have the opposite effect, the signal is blocked from that direction, and you have a weaker signal.

Get a grip, Harry, and quit arguing with everybody. You seem to have serious control issues. You are just wasting your time trying to change everybody's mind about everything they say.

My philosophy is this: Approximately 1/4 of the population is outright evil. I was more optimistic as a youth, but life experience has opened my eyes. They know what effect their actions have, and seek to harm others. Another 1/4 is so narcissistic that they cannot think in terms of anything except their own desires. They couldn't care less what effect their actions have upon others. Another 1/4 is too stupid to even realize what effect their actions have upon others. That leaves only 1/4 that could qualify for the definition of "good". You'll have to decide for yourself where you fit in.

Try as you might, there is nothing you can do about the others, you are simply outnumbered. (Just as I'm probably wasting my time here talking to you.) The sooner you realize this, the less likely you are to have a heart attack or stroke. Outlive 'em, it's the best revenge.

[HarryT]

Originally Posted by ThomasMc

It has nothing to do with windows, Harry. An ungrounded Faraday cage is an antenna. Put a radio next to a metal window screen, and you'll get better reception. That was a trick I learned in the 70s, with my short wave radio. It isn't because the radio waves are passing through the little holes, they are smaller than the wavelength of the signal. Ground that screen, and you have the opposite effect, the signal is blocked from that direction, and you have a weaker signal.

I stand corrected on the antenna issue. Thank you for the information. I don't know much about antennas, but I do know about Faraday cages, having been professionally involved with them in a "former life" when I worked as a physicist in the UK nuclear power industry.

Get a grip, Harry, and quit arguing with everybody. You seem to have serious control issues. You are just wasting your time trying to change everybody's mind about everything they say.

Not everything they say. There's a series of books published here - don't know if they are available elsewhere called "Teach Yourself <x>". They have a series motto, "Give a wise man knowledge, and he will be yet wiser". That seems to me to me an excellent philosophy to live one's life by. Perhaps it is futile, but it's worth the effort.

[ThomasMc]

Well, I suppose I could hope for nothing else, coming from a Dalek...

[BenLee]

Originally Posted by ThomasMc

It has nothing to do with windows, Harry. An ungrounded Faraday cage is an antenna. Put a radio next to a metal window screen, and you'll get better reception. That was a trick I learned in the 70s, with my short wave radio. It isn't because the radio waves are passing through the little holes, they are smaller than the wavelength of the signal. Ground that screen, and you have the opposite effect, the signal is blocked from that direction, and you have a weaker signal.

Get a grip, Harry, and quit arguing with everybody. You seem to have serious control issues. You are just wasting your time trying to change everybody's mind about everything they say.

My philosophy is this: Approximately 1/4 of the population is outright evil. I was more optimistic as a youth, but life experience has opened my eyes. They know what effect their actions have, and seek to harm others. Another 1/4 is so narcissistic that they cannot think in terms of anything except their own desires. They couldn't care less what effect their actions have upon others. Another 1/4 is too stupid to even realize what effect their actions have upon others. That leaves only 1/4 that could qualify for the definition of "good". You'll have to decide for yourself where you fit in.

Try as you might, there is nothing you can do about the others, you are simply outnumbered. (Just as I'm probably wasting my time here talking to you.) The sooner you realize this, the less likely you are to have a heart attack or stroke. Outlive 'em, it's the best revenge.

So true. Don't know about the exact percentages, but those four groups definitely exist.

It's the first type we have to watch out for. The second two types will probably self destruct. And the last type, the "good" people, are harder to find than diamonds. Must treat them like family once you do though.

[vxf]

Phones are not allowed on planes because talking would bother those sitting around you.

That, and the quick movement creates problems with the software that handles switching between cell phone towers.

Also, roaming is a problem in terms of billing, especially in fragmented markets such as Europe. Phone companies have a hard time figuring out how to bill you for a phone call that starts in France but ends in Germany.

I did gain a bit of an insider's view on one of my last jobs. But no, I am no engineer - I just did some consulting with a firm closely involved in the issue (my field is finance).

And, frankly, so many times I forget to turn at least one of my phones off - as I am sure do many other people... the simple fact that I am alive proves it's not going to drop a plane

By the way, since February 2009 Ryanair allows the use of cell phones on some of their flights.

[ThomasMc]

Originally Posted by vxf

Phones are not allowed on planes because talking would bother those sitting around you.

Since a significant segment of the population thinks they have to talk at 3 to 5 times normal volume when on the phone, they wouldn't be able to hire enough sky marshals to keep the peace if people were allowed to use their cell phones during the flight. I know it would certainly stop me from flying. It's bad enough having to put up with those jerks in restaurants.

[jbjb]

Originally Posted by ThomasMc

Harry, you are the most argumentative person on these forums. You argue even with the people who agree with you. It seems to be your only mode of communication. Chill.

On the contrary - Harry is being entirely reasonable.

You made a claim that Faraday cages only work when grounded - this is definitely incorrect. There will be zero net electric field inside a Faraday cage irrespective of whether or not it is grounded.

I pointed this out (politely, I hope - that was certainly my intent), and Harry kindly provided a reference to support my statement.

/JB