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Name: Nicola
Status: student
Grade: 9-12
Country: Bulgaria
Date: Fall 2012


Question:
Can you transmit electricity through air (wireless)? I have heard Nicola Tesla had tried such a thing, but I do not know if it worked.



Replies:
Nicola, You can transmit electricity through air. there was a video regarding a demo in which the speaker lights up a TV using this technique. I shall see whether I can locate it and if so I shall send the link to you. Best Wishes.

Mani


Certainly. The energy is carried by varying electric and magnetic fields. This is how radio and microwave transmission work. The principle is used in all sorts of applications, such as signal transmission, (radio, cellular telephone) and cordless charging.

Richard E. Barrans Jr., Ph.D., M.Ed. Department of Physics and Astronomy University of Wyoming


Hi Nicola,

It is not possible to transmit electrical power directly through the air. What can be done, however, is to transmit energy in the form of radio or (especially) microwaves, then convert the transmitted radio or microwave energy received, to useful electrical power. Unfortunately, this process is not very practical since usually, only a small percentage of the transmitted energy is captured by the receiver for conversion back to electrical energy. The remainder is wasted.

Regards, Bob Wilson


Nicola,

You may be surprised to find out that we regularly transmit electricity through the air, but probably not in the way you think about when you talk of Tesla. Radio waves have energy and transmit power, although in small amounts. Generally, though, we do not run our refrigerators from these sources of power, even though they are wireless. Even still, it does not mean we cannot think of ways to transmit power wirelessly. In fact, there are ideas that have been considered such as using microwaves to “beam” energy from one location to another, or using lasers to direct energy over long distances. Tesla, if I understand his work correctly, envisioned essentially energizing the atmosphere such that you could place an antenna in the air and draw enough power to run a city. All of these ideas could work in theory (even some versions of Tesla’s ideas using the earth as a surface conductor), but they generally have some serious drawbacks: Consider first that you are trying to power a city without having any particular location from which to draw power. In this case, you need to “energize” a large area of the city. If you are using microwaves, for example, you need to be able to tap into this source such that you can power your appliances. If you are powering your dishwasher, you might need 2000 Watts of power. This power must be present in the air to be collected, and so you would need an antenna big enough to collect this 2000 Watts. Consider that a typical microwave use about 1000 Watts, and you can imagine that you would need an antenna at least as big as your microwave to collect this amount of power. However, the power in the air would be so high as to cook everything in its path (including you)! Further, even if you overcome this problem, you have the problem that you are putting energy in so many places that do not use the energy. Much of the energy would be lost, and thus you would have a very inefficient power system. Even in the most optimistic visions of Telsa’s future, I think power loss and inefficiencies would be a major issue. Some recent work has demonstrated that there may be means to transmit energy wirelessly that can overcome some of the efficiency problems (see, for example, some of the work at MIT using electromagnetic resonance). This work may lead to some freedom from tangled power cords, although it is still in the early stages of development. Even should efficiency problems be overcome, it is not clear whether the concerns of health and safety with bathing large areas with significant powers could be overcome.

Kyle Bunch, PhD, PE



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