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Topic # 14764 19-Jul-2007 10:54 Send private message

Hey folks, I'm assuming you've heard that MIT has successfully powered a lightbulb wirelessly from a distance of a few metres. I heard that there was an energy loss of around 50%. My question is where did it go? Does that mean that there is a huge amount of static in the air? Just trying to get my head around this.




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Reply # 78791 19-Jul-2007 11:15 Send private message

Nikola Tesla first demonstrated 'the transmission of electricity without wires' in 1891. He was so ahead of his time that he was considered to be a 'mad scientist'.





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  Reply # 78799 19-Jul-2007 12:09 Send private message

Where lost energy always goes, heat!

It has been known for many years, as Jama points out, that power can be transported by changing magnetic fields but it is very inefficient.

What these guys did that was different I believe was to be able to make a directional beam

To answer you question essentially the high frequency oscillations of the magnetic field causes atoms in the air to move back and forth rapidly ,creating friction and therefor heat.

At no point is there "static" in the air




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  Reply # 78852 19-Jul-2007 19:42 Send private message

apparently you can transmit power using directed microwaves, i can't remember exactly how though, i'd assume that you use a detector or gunn diode.

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  Reply # 78868 19-Jul-2007 21:26 Send private message

mmm changes in flux...

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  Reply # 78886 19-Jul-2007 22:36 Send private message

There are plenty of ways you can transmit power without wires - most of them are impractical, inefficient or both however.

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Reply # 78905 20-Jul-2007 07:16 Send private message

Jama: Nikola Tesla first demonstrated 'the transmission of electricity without wires' in 1891. He was so ahead of his time that he was considered to be a 'mad scientist'.

I think he earned that reputation when he announced the invention of a 'death ray' in 1934 that was never substantiated and then went on to accuse governments of 'stealing his inventions'.

He was undoubtedly one of the most important scientists of our era but I think he may have been a little nutty towards the end.

As has already been pointed out, heat is generally the source of most inefficiency during energy transfer.



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Reply # 78916 20-Jul-2007 08:56 Send private message

Thanks for the replies. Heat makes sense. I wonder how much. In the demonstration there were several people seated between the power source and the light.

I love the idea of not having to plug my notebook or other devices in to charge and power them. A Wi-Fi powers source. Given that some people have used the power cables to transmit their network data, perhaps they could come up with a wireless work area that both provides your power and your comms through one source.

Given the heat generated as the the resistance to the signal, would it be more efficient in a hot environment, sorry if I'm being dumb geeky here, but this place is Geekzone after all.

As to Tesla, a mate of mine used to use that technology to photograph auras. Looked really cool.




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  Reply # 78922 20-Jul-2007 09:13 Send private message

They've been working on charging stations for notebooks using the same principle as cordless the rechargeable toothbrush (Inductive Charging). Same deal, you need more juice to get the job done due to loss. Uniden have a waterproof cordless phone that uses the same technology (AFAIK) and the power adapter is 21V as opposed to the non-waterproof model with a 9V supply.

Using the same technology in notebook computers will mean you can have the charging stations in the likes of a cafe or airport lounge, so a flat battery will no longer be an excuse to get out of work! There's no escape from work, so give up trying!

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  Reply # 78943 20-Jul-2007 10:33 Send private message

PDAMan:
Given the heat generated as the the resistance to the signal, would it be more efficient in a hot environment


More likely it would be more inefficient, as he temperature rises molecules in the air (and in the metal  of the transmitter and receiver ) vibrate more naturally so I would imagine it would be harder to get a consistent field.





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