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Author Topic: Is it possible to wirelessly transmit electricity?  (Read 2175 times)

Offline thedoc

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Loyiso asked the Naked Scientists:
   Is the wireless transmission of electricity possible - and if so when can we expect to see it?
What do you think?
« Last Edit: 13/04/2016 13:50:01 by _system »


 

Offline PmbPhy

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Re: Is it possible to wirelessly transmit electricity?
« Reply #1 on: 13/04/2016 15:00:47 »
Loyiso asked the Naked Scientists:
   Is the wireless transmission of electricity possible - and if so when can we expect to see it?
What do you think?
I'm sorry to report that this question is meaningless. In physics the term electricity refers to a set of physical phenomena associated with the presence and flow of electric charge. That's why in physics we can't speak of electricity as something in motion.

On the other hand layman use it to refer to a form of energy, i.e. electromagnet energy (EM), in which case it flows when an EM wave flows.
 

Offline Colin2B

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Re: Is it possible to wirelessly transmit electricity?
« Reply #2 on: 13/04/2016 15:26:09 »
It is possible to convert the electromagnetic wave PmbPhy mentions into electricity. It is already done in phone chargers.
It won't be seen for mains electricity distribution because the power requirements are too great for a practical, efficient system.
 

Online Bored chemist

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Re: Is it possible to wirelessly transmit electricity?
« Reply #3 on: 13/04/2016 19:41:45 »
Loyiso asked the Naked Scientists:
   Is the wireless transmission of electricity possible - and if so when can we expect to see it?
What do you think?
Yes it's possible, and it wasn't new technology when my dad was using it shortly after WWII
https://en.wikipedia.org/wiki/Crystal_radio

The first recorded observations of it were a lot earlier
https://en.wikipedia.org/wiki/Heinrich_Hertz#Electromagnetic_research
 

Online jeffreyH

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Re: Is it possible to wirelessly transmit electricity?
« Reply #4 on: 13/04/2016 20:16:48 »
It makes me wonder if this is what drove Tesla to search for wireless power transmission. Unless of course that notion of Tesla is more urban myth than fact.
 

Offline Craig W. Thomson

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Re: Is it possible to wirelessly transmit electricity?
« Reply #5 on: 14/04/2016 15:50:17 »
Something to consider: When a photon is travelling across space at the speed of light, there's an electric component in there, but no wires.

http://images.slideplayer.com/12/3517140/slides/slide_29.jpg
 

Offline Craig W. Thomson

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Re: Is it possible to wirelessly transmit electricity?
« Reply #6 on: 14/04/2016 16:05:36 »
Yes it's possible, and it wasn't new technology when my dad was using it shortly after WWII
https://en.wikipedia.org/wiki/Crystal_radio
Thanks for the post, that's pretty interesting. I think I remember hearing the term "crystal radio" before, but I sure didn't know that's where diodes came from. I actually used to have a galena specimen from Wyoming that I collected for a 9th grade Earth Science class.

http://geology.com/minerals/photos/galena-crystal-radio.jpg
 

Offline alancalverd

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Re: Is it possible to wirelessly transmit electricity?
« Reply #7 on: 14/04/2016 19:55:19 »
Loyiso asked the Naked Scientists:
   Is the wireless transmission of electricity possible - and if so when can we expect to see it?
Yes. The wireless transmission of energy is the basis of everything from ultralong wave radio to millimeter wave radar. The problem is that it is very ineffcient over long distances. You can detect the energy reflected from a laser beam or a radar pulse bounced off the moon, but it's a tiny fraction of what you transmitted, even with a really good laser and reflector.

Converting the received electromagnetic wave into a useful electric current is done by a tunede circuit, photomultipler, or whatever is appropriate to the received wavelength.   

Tesla experimented with near-field phenomena. You can sometimes see one such effect if you hold a fluorescent tube under an overhead power line, and some people have been prosecuted for stealing electricity through near-field induction, but the inverse square law means that unless you live right under the pylon, you will be most unlkely to cook your dinner with any  practical receiver.
 

Online Bored chemist

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Re: Is it possible to wirelessly transmit electricity?
« Reply #8 on: 14/04/2016 20:42:32 »
Loyiso asked the Naked Scientists:
   Is the wireless transmission of electricity possible - and if so when can we expect to see it?
. The problem is that it is very ineffcient over long distances.

you might want to discuss that with the people who make optical fibres.
"Attenuation loss can be as low as 0.2 dB/km in optical fiber cables"
from
https://en.wikipedia.org/wiki/Optical_fiber
 

Offline Craig W. Thomson

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Re: Is it possible to wirelessly transmit electricity?
« Reply #9 on: 15/04/2016 13:56:17 »
you might want to discuss that with the people who make optical fibres.
Try reading before you post. Here's what he said:

"The wireless transmission of energy is the basis of everything from ultralong wave radio to millimeter wave radar. The problem is that it is very ineffcient over long distances."

Now tell me, when was the last time you saw a wireless optical fibre?
 

Offline alancalverd

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Re: Is it possible to wirelessly transmit electricity?
« Reply #10 on: 15/04/2016 14:57:46 »
Loyiso asked the Naked Scientists:
   Is the wireless transmission of electricity possible - and if so when can we expect to see it?
. The problem is that it is very ineffcient over long distances.

you might want to discuss that with the people who make optical fibres.
"Attenuation loss can be as low as 0.2 dB/km in optical fiber cables"
from
https://en.wikipedia.org/wiki/Optical_fiber

That's why I stopped at millimeter radar!
 

Offline PmbPhy

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Re: Is it possible to wirelessly transmit electricity?
« Reply #11 on: 15/04/2016 16:06:21 »
Quote from: Bored chemist
Yes it's possible,..
Really? Please define the term electricity and a reliable the source of such a definition such as a physics text, EM text, physics handbook, etc.

I assume that you are using the term electricity as it would appear in, say, Webster's dictionary and assuming that the OP is a layman and is thinking of it in layman's terms and as such you were using it in that context. Is that correct? If not then please demonstrate where I was wrong when I explained that electricity is a set of physical phenomena associated with the presence and flow of electric charge. Thank you.
 

Online Bored chemist

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Re: Is it possible to wirelessly transmit electricity?
« Reply #12 on: 15/04/2016 18:49:53 »
you might want to discuss that with the people who make optical fibres.
Try reading before you post. Here's what he said:

"The wireless transmission of energy is the basis of everything from ultralong wave radio to millimeter wave radar. The problem is that it is very ineffcient over long distances."

Now tell me, when was the last time you saw a wireless optical fibre?
All the optical fibres I have seen have been wireless.
They are usually made of glass or plastic.
The wiki page I posted included hair and even water jets as examples.
Meanwhile, here's what wire means.
wire
wʌɪə/Submit
noun
1.
metal drawn out into the form of a thin flexible thread or rod.
"a coil of copper wire"
2.
an electronic listening device that can be concealed on a person.
"an undercover police informer who was wearing a wire"


So, one is metal and the oterh isn't.
Did you think you had a point?
 

Online Bored chemist

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Re: Is it possible to wirelessly transmit electricity?
« Reply #13 on: 15/04/2016 18:52:49 »
Quote from: Bored chemist
Yes it's possible,..
Really? Please define the term electricity and a reliable the source of such a definition such as a physics text, EM text, physics handbook, etc.

I assume that you are using the term electricity as it would appear in, say, Webster's dictionary and assuming that the OP is a layman and is thinking of it in layman's terms and as such you were using it in that context. Is that correct? If not then please demonstrate where I was wrong when I explained that electricity is a set of physical phenomena associated with the presence and flow of electric charge. Thank you.
I never said you were wrong about that did I?
I was just answering a lay-terms post with a lay-terms answer.

 

Online Bored chemist

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Re: Is it possible to wirelessly transmit electricity?
« Reply #14 on: 15/04/2016 18:54:38 »
Loyiso asked the Naked Scientists:
   Is the wireless transmission of electricity possible - and if so when can we expect to see it?
. The problem is that it is very ineffcient over long distances.

you might want to discuss that with the people who make optical fibres.
"Attenuation loss can be as low as 0.2 dB/km in optical fiber cables"
from
https://en.wikipedia.org/wiki/Optical_fiber

That's why I stopped at millimeter radar!

Nice try,but the "it" in the sentence I cited refers to wireless transmission, rather than a range of applications and wavelengths.
 

Offline PmbPhy

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Re: Is it possible to wirelessly transmit electricity?
« Reply #15 on: 16/04/2016 05:00:52 »
Quote from: Bored chemist
I never said you were wrong about that did I?
Where did I imply that I was making such an accusation?
Quote from: Bored chemist
I was just answering a lay-terms post with a lay-terms answer.
No need to be so defensive. I contend that your responses is incorrect and misleading. But I was curious as to what definition you used such that electricity is meaningful for it to be able to move.

In response to the question I replied
Quote
I'm sorry to report that this question is meaningless. In physics the term electricity refers to a set of physical phenomena associated with the presence and flow of electric charge. That's why in physics we can't speak of electricity as something in motion.
and you replied
Quote
Yes it's possible,  and it wasn't new technology when my dad was using it shortly after WWII
The question was about the wireless transmission of electricity, not about electromagnetic waves.

As I explained in my response, the term electricity is defined in Webster as follows.
http://www.merriam-webster.com/dictionary/electricity
The layman's term (i.e. the simple definition) is as follows
Quote
1) a:  a fundamental form of energy observable in positive and negative forms that occurs naturally (as in lightning) or is produced (as in a generator) and that is expressed in terms of the movement and interaction of electrons

b:  electric current or power
That is certainly different from an EM wave. When layman use the term electricity they mean the flow of current as in their household wiring. However

However physicists rarely use that term but if they do they usually mean
Quote
2) a science that deals with the phenomena and laws of electricity
(definition #3 does not apply to the question). See also https://en.wikipedia.org/wiki/Electricity
Quote
Electricity is the set of physical phenomena associated with the presence and flow of electric charge. Electricity gives a wide variety of well-known effects, such as lightning, static electricity, electromagnetic induction and electric current. In addition, electricity permits the creation and reception of electromagnetic radiation such as radio waves.
...
In none of these definitions can "an electromagnetic wave" be found. However I giving you the opportunity to show me that you knew of another definition which I may not be aware of. Nowadays I prefer to ask people what they mean when it comes to terminology rather than merely state emphatically that they're wrong, like I would normally have done otherwise. But even what the term means to the layman it isn't an EM wave.
 

Offline highvoltpower

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Re: Is it possible to wirelessly transmit electricity?
« Reply #16 on: 16/04/2016 07:17:47 »
Itís possible to transmit power wirelessly, but it is extremely useless. It might work to power small devices over short distances.
 

Offline Craig W. Thomson

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Re: Is it possible to wirelessly transmit electricity?
« Reply #17 on: 01/05/2016 15:15:40 »
All the optical fibres I have seen have been wireless.
They are usually made of glass or plastic.
The wiki page I posted included hair and even water jets as examples.
Meanwhile, here's what wire means.
wire
wʌɪə/Submit
noun
1.
metal drawn out into the form of a thin flexible thread or rod.
"a coil of copper wire"
2.
an electronic listening device that can be concealed on a person.
"an undercover police informer who was wearing a wire"


So, one is metal and the oterh isn't.
Did you think you had a point?
No, I KNOW I had a point:

wire∑less
ˈwī(ə)rləs/
adjective
1.
using radio, microwaves, etc. (as opposed to wires or cables) to transmit signals.
"wireless broadband"

Now, do I need to post the definition of "cable" for you as well? You do know glass, plastic and hair aren't part of the electromagnetic spectrum, right?
« Last Edit: 01/05/2016 15:18:24 by Craig W. Thomson »
 

Offline quandry

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Re: Is it possible to wirelessly transmit electricity?
« Reply #18 on: 06/05/2016 11:02:44 »
My goodness. Don't people like to make life complicated.
The answer to the question is yes.
In wireless power transfer, a wireless transmitter connected to a power source conveys the field energy across an intervening space to one or more receivers, where it is converted back to an electrical current and then utilised.
Marconi is well known for doing this in the early days. It is called Radio.
Tesla spent some time doing this to light incandescent bulbs.
It is currently being used to (amongst other things) charge cellphone batteries.
 

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Re: Is it possible to wirelessly transmit electricity?
« Reply #18 on: 06/05/2016 11:02:44 »

 

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