Wireless charging relies on magnetic induction technology. The electromagnetic waves emitted by the charger can pass through certain non-metallic surfaces such as plastic or wood to reach the device to be charged.
Wireless charging works through the principle of electromagnetic induction, discovered by Michael Faraday. Basically, it's simple: a coil connected to a power source creates a variable magnetic field. When you place your phone equipped with a second coil nearby, this magnetic field automatically generates an electric current in the phone. It is this induced current that charges the battery, all without any cables. No magic, just physics. The closer and more aligned the coils are, the better the energy transfer.
The physical properties of the material between the charger and the device play a key role. Surfaces made of plastic, glass, or wood (as long as they are not too thick) allow the electromagnetic field to pass through easily. On the other hand, forget about surfaces made of metals like aluminum or steel: they strongly block or disrupt energy transfer. The thickness of the material also matters a lot: even a surface that allows current to pass well may lose efficiency if it is too thick. The ideal is a thin, non-metallic surface without significant roughness or internal defects to avoid unnecessary losses and heating.
The frequency of electromagnetic waves greatly affects their ability to penetrate a surface. At low frequencies, such as those used in wireless charging (a few tens to hundreds of kHz), the waves easily penetrate non-conductive and non-magnetic materials like plastic, wood, or glass. But as the frequency increases, the waves become more sensitive to obstacles. At high frequencies, they tend to be absorbed or reflected more by even relatively thin materials, quickly losing power. This is why wireless charging systems generally maintain relatively low frequencies: it allows for good penetration of common materials while minimizing energy loss.
The quality of the magnetic coupling between the transmitting and receiving coils is crucial for effective wireless charging. Essentially, the better the coupling, the less energy you lose. The more precisely aligned and closer the coils are to each other, the better the magnetic flux, and the more efficiently the energy transfers. Resonance is somewhat like when you try to push a swing: you give just the right push at the right moment to increase the speed without too much effort. When the two coils operate at a common resonance frequency, energy flows more easily even if there is a small distance or surface between them. It is thanks to this resonance that some wireless chargers allow you to charge your phone through tables or thick stands.
Wireless charging is convenient, but let's be frank, it's far from perfect. First, there's the distance: the further you move your device away from the charging pad, the less effective it becomes. The power drops off quickly as soon as you exceed a few millimeters. Then, there are thick, metallic, or magnetic materials that seriously disrupt the magnetic field and drastically reduce the transmitted energy. As a result: energy loss, unnecessary heat, and much slower charging. To optimize all this, manufacturers rely on precise coil alignment, controlled increases in the magnetic field frequency, and above all, specific low-absorbent materials. Finally, increasing the number of charging coils (multi-coil chargers) helps facilitate alignment and offers better positioning freedom for your smartphone.
Contrary to popular belief, most non-metallic surfaces such as wood, plastic, or glass provide very little resistance to the magnetic field, thus facilitating the wireless charging of your smartphone.
Electric toothbrushes were among the first consumer products to adopt inductive charging in the 1990s, long before your mobile phone did!
Did you know that increasing the frequency used in wireless charging theoretically allows for a reduction in the size of the necessary coils, but conversely leads to an increase in energy losses?
The Qi standard, now widely adopted by the industry for the wireless charging of mobile devices, derives its name from the Chinese term "Qi" (pronounced "Chee"), meaning vital energy or energy flow.
Currently, no scientific studies have demonstrated a significant danger associated with the regular use of wireless charging. It uses relatively low frequencies and power levels that have been tested and deemed safe for daily use according to international industry standards.
Yes, too much thickness can reduce the efficiency of wireless charging by decreasing the intensity of the transmitted electromagnetic field. For optimal charging, it is recommended to keep the surface as thin as possible.
Sure! Here’s the translation: "Yes, by carefully selecting materials (non-conductive, thin, and with low absorption), or by precisely positioning the emitter and receiver closely together, one can significantly optimize its efficiency. Additionally, using systems with appropriately tuned frequencies and enhanced resonance also contributes to increasing the efficiency of energy transfer."
A slight warming of the wireless charging device is normal due to energy losses through induction. If the surface being used absorbs or partially blocks electromagnetic waves (for example, certain cases or less suitable materials), this can increase the heating effect due to a less optimal use of the transmitted energy.
No. Although the charge by electromagnetic induction passes through most non-conductive surfaces such as plastic, wood, or glass, it is blocked or significantly weakened by conductive materials, particularly metals.
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