I have a question about wireless charging. I know that wireless charging works by sending power through em waves, which cant be converted by the human body enough to feel any kind of shock, but what about if high power wireless charging were to become a thing? Would standing between the pathway of the charger and reciever of a high power wireless circuit send a lethal portion the electricity through you if the power were high enough? Or would the amount of power from the circuit being converted by the human body never become dangerous enough no matter how much power was being transferred wirelessly to the receiving end?

 

High magnetic fields are used in medical imaging and the patients can’t even feel it, let alone be harmed by it. Of course you wouldn’t want to live in it.

 

I know that wireless charging works by sending power through em waves, which cant be converted by the human body enough to feel any kind of shock, but what about if high power wireless charging were to become a thing?

Depends on what constitutes "high power."

Would standing between the pathway of the charger and reciever of a high power wireless circuit send a lethal portion the electricity through you if the power were high enough?

(See above)

Or would the amount of power from the circuit being converted by the human body never become dangerous enough no matter how much power was being transferred wirelessly to the receiving end?

"Never" is a tricky word. I'm sure if you got between transmitter and receiver in a wireless power system transferring multi-megawatts, you'd end up a crispy critter in short order. Hundreds of kilowatts? Maybe. A kilowatt? My guess (with fingers crossed) would be probably not. Below that? I would be surprised to see any ill effects.

Wireless power transfer works by induction, and in effect the transmitting and receiving coils simply form an air-core transformer tailored to the task at hand. The transmitting coil emits an oscillating magnetic field which then induces an oscillating voltage in the receiving coil; this voltage is then rectified and filtered to produce DC. Your body is not a coil, but rather an odd-shaped lump of (slightly) electrically conducting meat; so you're not likely to develop much voltage or dissipate much power.

 

However, if you have any metal implants, watch out. The changing magnetic field induces eddy currents that can cause significant heating. I recently read the Qi spec for wireless charging, and transmitters are required to detect if someone has thrown in metal object onto the charging pad and shut down because it could otherwise heat it up to and unsafe temperature. And we are talking only a few watts here.

Bob

 

However, if you have any metal implants, watch out. The changing magnetic field induces eddy currents that can cause significant heating. I recently read the Qi spec for wireless charging, and transmitters are required to detect if someone has thrown in metal object onto the charging pad and shut down because it could otherwise heat it up to and unsafe temperature. And we are talking only a few watts here.

Bob

That's why people with peacemakers cannot have magnetic resonance imaging done to them.
That also means that wireless high-power charging isn't going to be a thing, or at least not if by magnetic transfer or RF.
Even something like this will have a (likely very low) limit on how much power they can get into a focused beam of light: https://www.wi-charge.com/technology/

 

I certainly felt the effect of the magnetism when I had an MRI of my shattered shoulder quite a few years ago. It pushed on the iron in my blood and it did not feel good at all. But that was probably because the damaged area was very sensitive.
A conductor in a changing magnetic field will indeed have a voltage generated and a current circulating. I can't say if it will cause damage, but the folks selling wireless charging systems deny that it happens. BUT I have been lied to before.

 

That's why people with peacemakers cannot have magnetic resonance imaging done to them.
That also means that wireless high-power charging isn't going to be a thing, or at least not if by magnetic transfer or RF.
Even something like this will have a (likely very low) limit on how much power they can get into a focused beam of light: https://www.wi-charge.com/technology/

Even if wireless high-power charging was a thing would you want to pay and could the utility handle the much higher electric requirements compared to a wired connection if the efficiency was in the optimistic average range of about 70%. A qi charger might require ~2A in order to output 1A, imagine that with a toaster oven (1,200 watts) or the extra wireless power requirements for a city full of air conditioners on a hot day.

 

Even if wireless high-power charging was a thing would you want to pay and could the utility handle the much higher electric requirements compared to a wired connection if the efficiency was in the optimistic average range of about 70%. A qi charger might require ~2A in order to output 1A, imagine that with a toaster oven (1,200 watts) or the extra wireless power requirements for a city full of air conditioners on a hot day.

Imagine recharging an EV battery, one of those 120 mile range ones, in an hour. 120kwH delivered in an hour. Now even at 90% efficiency that is a whole lot of power going someplace other than the battery. That is where the persistent lies are found, that all of that energy just vanishes. NO, it goes someplace doing things we would choose to not have done. Thus the challenge to the engineers: Yes, you could do it, but NO, it is not a good idea to do it.

 

Well, maybe if the distance is really short, and there are safety measures to make sure that the magnetic field is contained (like if it were two parts of a transformer). They're trying to make wireless chargers for electric cars, so i suppose that it's a matter of waiting to see what happens: http://www.qiwireless.com/electric-cars-industry-wireless-charging-standard/

Still, unless it's very efficient, i don't think that opening a lid, getting a big plug hanging in the wall and connecting it there is very much of a hassle. I suppose that electric cars have a safety that prevents them from moving if you forget to disconnect the charger, so that there aren't any unintended fireworks.

 

The problem is that the marketing people are targeting the group that would indeed find plugging something in "a great big hassle" , and would be happy to pay a lot more for something more convenient no matter how much less efficient it was. I think that the root of their problem is the inability to focus their attention long enough to complete the task. Eventually the lack of ability to focus attention will probably destroy much of civilization, or at least the part with freedom. At least that is how I see it. Any teacher can verify that the present attention span is far to short.

 

Wireless charging is just another form of a transformer. As has already been stated, the primary (charging pad) produces a magnetic field and the secondary (device being charged) changes the magnetic field into electricity.

Transformers work on this principal. Depending on how the transformer is constructed, a transformer can lower the voltage and increase the amperage or can increase the voltage and reduce the amperage. MOST transformers (in the traditional sense) have iron cores because the iron is best at transmitting that magnetic energy. However, there ARE such things as "Air Core" transformers (someone already mentioned that too). They are much less efficient at transmitting magnetic fields from one source to another (charger to receiver). Use in low power systems, the loss of energy is not significant and therefore they can be made to work well enough for charging your cell phone or other wireless charged devices such as a toothbrush. But at high power (as you may be thinking of) the losses would be enormous and terribly wasteful. It's not likely you're going to see much in the ways of wireless power transmission for quite some time, until some discovery comes along to change that.

Radiographic ovens and other local heating devices use magnetic waves to induce electrical currents in a metal causing it to heat up. Doing so can be used for welding two parts or can be used as a means of heating something to very high temperatures and melting it. I've seen these ovens recover scrap copper, there are plenty of videos on YouTube if you want to have a look.

But in a nut shell, getting between two charging pads isn't likely going to cause any bodily harm.

 

Consider the legislation that changed the efficiency requirements for wall wart power devices. They do not waste much power individually, but overall it was deemed a large waste problem. Hence new rules about efficiency and power consumption.

 

Wireless power through a laser could definitely do damage to a person in the path!

Bob

I certainly felt the effect of the magnetism when I had an MRI of my shattered shoulder quite a few years ago. It pushed on the iron in my blood and it did not feel good at all. But that was probably because the damaged area was very sensitive.
A conductor in a changing magnetic field will indeed have a voltage generated and a current circulating. I can't say if it will cause damage, but the folks selling wireless charging systems deny that it happens. BUT I have been lied to before.

As I stated, the spec for wireless chargers requires them to detect a metal object and cut off.

Bob

 

Wireless power through a laser could definitely do damage to a person in the path!

TS states "EM" transmission. This would preclude considering lasers and microwave transmissions.

I know that wireless charging works by sending power through em waves • • • ?

 

TS states "EM" transmission. This would preclude considering lasers and microwave transmissions.

How so? Lasers and microwaves both are EM waves.

Bob

 

OK, I suppose microwaves are. Lasers? Isn't that basically light? And high intensity light can burn.

My take on what the Thread Starter was talking about was the magnetism that is created by wireless chargers; chargers of cell phones and toothbrushes, and anything else being charged by electro magnetic coupling.

 

The way to solve the wireless charger problem........is with a charging dock. Drop it in. Pull it out.

EM waves are too weak. EM fields don't like air.

If one could immerse the RXer in a sand or rice like.....high mu media......maybe wireless might work.

Or just drop RXer in a charging dock.

 

The way to solve the wireless charger problem........is with a charging dock. Drop it in. Pull it out.

EM waves are too weak. EM fields don't like air.

If one could immerse the RXer in a sand or rice like.....high mu media......maybe wireless might work.

Or just drop RXer in a charging dock.

I cooked my dinner with EM waves in my microwave oven. Low power is low power, but HIGH power is just a lot more of the same thing. AND, please consider that those folks who get so very upset about the EM fields may have some actual basis for their concerns. WE don't know everything that there is to know just yet.

 

To the TS original point, I am and would be concerned with being in a strong EM wave. I am much more leery than the average person about broadcasting microwaves down my ear-hole. Not to mention a usec of gamma wave from outer space.

Especially as these phone frequencies go up. As for fields......with my stents.....I don't play with large super magnets. And I had some nice big ones, but gave then away.

As for the microwave comparison.....it's apples and oranges. We don't want to use 600-1000 watts to charge a smartphone do we? Maybe MisterBill2 has the solution. People would do that. Stick the phone in the MW for 60 sec.

It would be called a miracle. Even at 5 min. A few of the guys on site should get on this. Everyone has a MW.

I just think that with present materials, tech and knowledge....it's not worth it. There are situations where this process is necessary. A barrier or separation with no contact available.

They are always improving it. It might be easy peasy and cheap in the future.

 

I had a few MRI's done recently. One came with horrific pain. They sent me home to try again. I pre-medicated with stuff I already had and designed the doses to peak at the time of the MRI. I also asked the tech to restrain my arm. It still hurt, but not as much. They were imaging the cervical spine and my arm hurt with very sharp pain. The non-oral med I used was a Lidocaine patch and some other oral Rx meds.

If you close your eyes before going into the chamber, the claustrophobicness goes away. Then it usually just the noise.