Re: How wireless electricity works?

Good question! It looks like "magic" but it isn't. Indeed, it is actually 
very old technology, as technology goes. Indeed, one could suggest that 
wireless electricity has been around since Faraday's time.



And as you point out, Tesla was able to transmit electricity through the 
air. There is a cost to this, though, and that is often glossed over in 
explanations.



Essentially, "wireless electricity" isn't wireless. Instead, it relies on 
two coils of wire that are not connected. The first coil uses electricity 
to generate an alternating magnetic field. The second picks up that 
alternating magnetic field and uses it to generate electricity. Really, it 
is a demonstration of the fact that "electromagnetism" or the 
electromagnetic force essentially says that electricity and magnetism are 
one and the same. They are two sides of the same coin.



Perhaps taking a step backwards might help. How do we generate electricity 
in, say, a hydroelectric dam power plant? The answer that you will usually 
find is "with a generator" but then the question becomes what is a 
generator? At it's heart, a generator is a rotating magnet inside a coil. 
The magnet generates magnetic induction in the coil. As the magnet 
rotates, the magnetic induction drags the electrons in the coil with it. 
(Okay, that is simplifying things but will work for now.) It is the flow 
of these electrons that represent the current of the electricity. With a 
fixed magnetic, we can create direct current and run a light bulb, for 
example. Bicycle wheel generators used to be used to light up a bike lamp 
based on this idea.



However, a more efficient method of transmitting electricity is to use an 
alternating current. This requires that the magnetic field switches 
polarity as it rotates inside the coil. More accurately, both the north 
and south poles of the magnet are inside the coil and spin as the magnet 
rotates. The resulting voltage and current are "alternating current" and 
can be made much stronger. Alternating current does not exhibit the same 
level of power loss that direct current does. There are great stories 
about the fight between "alternating" and "direct" current with Tesla 
backing the latter. In the end, he lost the debate because alternating 
current is more efficient for transmission over large distances.



What has this to do with "wireless electricity"? In essence, the magnetic 
induction in a wireless device operates in the same manner except that the 
rotating magnetic is replaced by an oscillating (or "rotating") magnetic 
field generated by electricity. The two circuits are connected by this 
magnetic induction.



So your next question is about a home-made project. I suspect that it 
might be one describing how to make a wireless electrical device from old 
television parts or such. Not necessarily a good idea as the components 
inside even an old television that has been left unplugged for a long time 
might still be quite shocking! That said, if I look at the plans for such 
a device on the Internet, it used a battery and the purpose of the NPN 
transistor is to generate an alternating field. Without the alternating 
field (without a circuit that can both flip and amplify the voltage), you 
don't get the magnetic induction that you need to transmit the energy. 
There are other ways of doing this but all involve some form of circuitry 
to generate an appropriate field.



As to your final question, yes, Tesla was able to transmit electricity 
throughout his grounds. Some accounts even suggest that he was able to 
light fluorescent light bulbs up 27 miles away. The latter is a dubious 
claim as the power requirements would have been quite prodigious. The 
leakage alone would have been damaging to anyone nearby. The energy losses 
are huge and not practical. But in small, enclosed space it is possible to 
light up fluorescent lights using a Tesla coil or similar device.



The really exciting work in this area is centered around finding 
mechanisms to connect to devices without broadcasting electromagnetic 
waves in all directions. There is lots of work being done - just think of 
the possibilities involved if you could fly a plane or launch a rocket 
without having to carry a fuel supply. Wireless transmission could be the 
way of the future but for now, it is pretty much limited to toothbrushes 
and cellphone charges.



Hope this helps!