Hello guys,
In this article, I will go over how exactly wireless charging works on smart phones and other device we use every day and I really want to explain the physics behind this because it's pretty simple. It might seem like magic, but the physics principles are something you would learn in any intro physics course dealing with electromagnetism. I'm going to go over that today and you shouldn't have a problem understanding.
How does wireless charging work?
Basically, wireless charging usually takes advantage of something called electromagnetic induction.
By Faraday's law of induction, this basically says that when you take a loop of wire and put it into a changing magnetic field, it induces a current in that wire. With wireless charging, there’re two parts:
- The base station (Transmitter),
- The object or device being charged (Receiver).
In the base station, there is a coil that has an alternating current going through it and because of this alternating current, any wire that has a current going through it has an electromagnetic field going around it. When the charging station has the current going through it, it's creating an electromagnetic field and because it's alternating current, it's going back and forth, so this is a changing magnetic field.
]On the device side, you have another coil which is in that changing magnetic field, that's why you must be close to the charging station or else the magnetic field won't be strong enough.
Once that device is in that magnetic field, the field induces another current into the device which causes it to be able to charge. At this point, you have a current going through the phone and of course it is an AC current, so it must be converted to DC current which can charge the battery.
You might be wondering how the electricity passes from the charger to the phone if they don't make contact.
How do the electrons get from one side to the other if there's no conductive material?
In reality, not a single electron passes from the charging station to the phone, so how does that make sense? How do you get the energy to store into the phone?
You don't have to transfer the electrons, they're already there as free electrons in the phone. They just need to be rearranged so they become useful.
After the alternating current (AC) is induced into the phone's coil, it gets converted into a direct current (DC) which is more useful by basically rerouting half of the alternating current into one direction but all you have to know is that the alternating current is rerouted in such a way that it becomes a direct current, so instead of alternating, it goes in one single direction just like as if you had plugged it into a charger into the wall where the wall alternating current gets converted into a direct current and is plugged into the phone directly.
It's the same idea, all you must know is that by the time the current gets to the battery, it's in a single flow and a single direction as direct current. In your phone's battery, there's a lot of chemistry going on and that's really the source of the energy.
When your phone is charged, there's an electric potential difference between one side of the battery and the other. This simply means that the electrons on one side of the battery are happy and the one on the other side isn’t happy because they want to get to the other side. When it's fully charged, they're in a place where it's not in equilibrium, the electrons want to get to the other side, so you have a lot of energy stored up because the electrons will just automatically go over to the other side if you let them.
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[Electric potential difference between one side of the battery and the other.]
When you go to do something in the phone which is anything that requires energy, you're basically allowing the electrons to go from one side to the other. Eventually, as the battery dies, all the electrons have gone to the other side and they reach equilibrium, they're happy with where they are, so you can't harness any more energy from them.
But when you get a DC current whether it's wired or wireless, you basically create a new electric potential in the reverse direction which causes the electrons to want to go back to the other side.
That means when they get to the other side, they're useful again and they're stored. It's not that you're getting electrons just to be used up and they disappear but rather, you're getting energy from the movement of the electrons. It's not like they just go away forever, they're just being rearranged so they become useful.
It really doesn't matter how you get the electrons to move from one side of the battery to the other, you can use it from plugging it directly into the wall and inducing it that way or you can do it from a wireless charger. The effect is the same, you're creating an electric field which moves the electrons over.
Where does the initial energy, not the electrons but the energy come from?
It comes from the power station. The power station has basically what you can think of as pumps on the other side which churns the electricity and the electrons back and forth. All they're doing is moving the electrons back and forth and then you can harness that movement and redirect it into any of your devices but none of the electrons are being transferred to stay into your devices. Your devices already have those three electrons stored up, they're just not in the right place, so that's where the energy from the wall comes from, you're not taking electrons out but you’re simply using the energy.
]Think about this analogy: A grandfather clock where the energy is stored in the position of the weights, as you pull down on a lever using your muscles energy, the weights get higher up in the body of the clock and they want to go lower, they want to go from the higher potential which is higher up to lower potential near the ground but obviously, they can't just drop down because you're holding it back to be used as energy to swing the pendulum.
It's kind of like the electrons which can be reused and stored on one side of the battery until they're transferred to the other and used up. It's not like you're using up the weights as they drop at the bottom, you can put them back.
That's how you can think of it like the weights are like the electrons and they can be reused if you have external energy whether it's your muscle putting the weights up against gravity or it's the power station which creates electromagnetic field to push the electrons back across the battery. That's why you don't need a physical connection between the power source and the device because no actual electrons are transferred but the energy.
I hope I explained it in a way that made sense and was interesting to you guys, so I want to know what you guys think if this explanation made sense at all, let me know by replying this post and don’t forget to click that upvote button and watch it spin till the end.
References: 1 - 2 - 3 - 4 - 5
Image sources: 1 - 2 - 3 - 4 - 5 - 6 - 7
Thanks to 
for this amazing toon.
