Wireless chargers work by creating a magnetic field that your phone, watch, or other device absorbs to gain energy. When you place a device on a wireless charging pad, a small coil in the device receives and harvests energy from the magnetic field, and uses it to power the battery. Wireless charging is a hassle-free way to charge your device, but the technology currently has a few drawbacks, such as being slower than the ordinary cables.
While wireless charging may seem like a recent invention, its origin comes from more than a hundred years to the popular Serbian-American inventor, Nikola Tesla. In the late 1800s, Nikola Tesla successfully transmitted electricity through the air. He used a process called resonant-inductive coupling, which works by creating a magnetic field between a transmitter and a receiver sending electricity respectively to power light bulbs in his New York City laboratory. He patented the Tesla coil, which is a tower with a coil that shoots out bolts of electricity. Tesla planned for much greater wireless power grids, but never came to reality.
The same principle of inductive charging applies to smartphone wireless charging. An electromagnetic coil, the induction coil in a charging base, creates a magnetic field and is basically an antenna to transmit a field of energy. A second smaller coil in the phone receives and and harvests the energy and it’s circuitry converts it back to usable energy for the battery.
In recent years, wireless charging technology has come a long way: Charging speeds have increased and designers have established a Qi standard allowing multiple products to be compatible with various chargers. However, phones aren’t the only things using the wireless capabilities; medical implants like pacemakers are also recharged wirelessly.
There are also a few drawbacks regarding this advanced tech. For starters, it is much slower and much less efficient as the further it is away from the transmitter, the less energy it will receive from the magnetic field. Phones require so much energy that the charging must be within millimeters of the device. "This field drops off really quickly," he said. "It still has a little bit of energy after two centimeters, five centimeters. At 10, it's just like, nothing. If you had a coil the size of a desktop, you could probably hold it a foot above the desk, but you'd be using a lot of power. That's the big problem with wireless charging in general. The research is trying to increase the efficiency of charging, or make our phones more energy efficient."
While this makes wireless charging limited for phones that use a lot of power, it isn't as challenging for smaller devices like Radio-frequency identification (RFID) tags that use less power. The difference in energy between the two, if you think about them in terms of mass, is like an African elephant versus an ant, Hester said. "Wireless charging and the energy efficiency of computation are both going up, so we're taking advantage of those two things at the same time," he said. "What I could do for the same amount of energy 20 years ago, I could do way more now, so you don't need as large a battery." In other words, although wireless chargers are relatively weak now, they'll get better every year.
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References:
“A Full Guide to Wireless Charging, Including How It Works and the Best Models to Buy.” Business Insider, 6 Jan. 2021, www.businessinsider.com/how-does-wireless-charging-work?international=true&r=US&IR=T.
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