Wireless Energy transfer

Wireless Energy transfer:-

Briging AC up, here's another use. Last month or so, a team of engineers in MIT successfully powered up an electric bulb using wireless energy transfer. With matching coils for transmitter and receiver, they were able to transfer very high range magnetic energy and power up the desired device.

Reason for using magnetic energy is most of the world is electrically conducting to some degree but magnetically inert and magnetic energy being a convertable form can be readily used to generate electricity.

Just a thought to ponder upon

That's exactly how transformers have been working since years. The energy transfers between the primary and secondary windings through a magnetic field.
The MIT engineers were only able to do it wirelessly for a few meters or so. We can consider it as a wireless transformer with the core being air. Most probably they were using a high frequency alternating magnetic field.
The concept is still very inefficient because they might have spent a hell lot of energy generating that strong magnetic field than what is required to light a bulb through simple pair of conductors. Things will be promising when they are able to do such a thing more efficiently and hence transmit energy to greater lengths.

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one more funny question. If the MIT engineers use such a strong magnetic field then won't the transmitter attract metal objects towards it? It is like a strong electromagnet right? Won't the electronic devices around it malfunction? e.g. most CRT TVs show a distorted image when a small magnet is brought close to the picture tube.

a. MIT engineers did not use a large magnet to transmit energy. The fundamental is "quite close to" transformers, but not exactly like it. Just close.

b. Energy is transmitted by EM waves, and not just the magnetic field.

Here is the tinkering with another funny question part -

In Transformer the actual field that dies of for inverse squared for distance it is used. In case of EM waves and resonant high gain antennas, we can use something called as transfer modes (There are two kinds - transfer electric and transfer magnetic modes - Namely TE and TM. TE00 is the most basic mode used in/describes isotropc antenna EM pattern). The EM waves and antennas have properties that can make them "high gain" by these properties. So no need of a big magnet. No need to worry about getting things attaracted to the device.

Now the part that I mention also is that people at MIT actually used magnetic resonance, because most things are magnetically inert. Another such device is a CT scanner. People usually dont carry iron crutches close to the CT scanner but everything else is just as easily allowed in that room as in any other ward of hospital. Because even though that ONE piece of magnet packs field capable of the strength of 10 earths, it is in a world that is magnetically nuetral. Thats my understanding - please comment if you think otherwise...

AC funny question + answer:

AC funny question + answer:-

nobody answered it till now. let me answer it :-).
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Q) What really is a funny quiz question perhaps is - Current is defined as "Charge flowing through a conductor" in +2 physics books. Now in AC, typically an electron in power transmission wire moves merely 10 atoms far to a direction when it is called back to oscillate again back and forth. So question is if this electron never reached the bulb in my house, how come it glows?

Ans) Imagine there is a long pipe (the wire) that is completely filled with water (the electrons). Now what will happen if i push the water a little from one end of the pipe. The water on the other end of the pipe will immediately push forward. The reverse happens when i pull back the water. So even though the water molecules at one end of the pipe have not reached the other end, the molecules at the other end have moved back and forth. Thus energy transfer has taken place (i.e. moving of water molecules). I could use this energy to do some work, (e.g. turn a propeller).

This can also answer the 2nd funny question below
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Q) In case of Direct current, electrons move in a copper conductor at a speed of only 1/4mm per second. For such a slow speed it will take an electron several minutes to travel a few inches of wire between the battery and the bulb. How come then does the light bulb turn on instantaneously?

:-)

parabolic shape of rx antenna

parabolic shape of rx antenna......:-

For a rx. antenna it is necessary to accumulate signals in a greater extent ,so that the beam area under the major beam lobe as much as possible. in parabolic reflecting antennas a property of light is being used, the reflective property. as the antenna is parabolic in nature, when signals fall in the dish, the dish reflect the signal in a converging manner. at the center of the antenna a sensor (receiver) is placed and it get the signal with high intensity... so a high accuracy signal is being received.

But, in some cases yagi uda antenna is also used as rx. , because it is mainly an array of antenna(BSA or EFA), so its efficiency can be manipulated by adjusting the no. of array elements.........again, the size of an antenna should be optimized according to its efficiency.....