Inductive Wireless Charging

If you wave your hand vigorously next to a toy boat floating on water, ripples form and make the boat rock on its own. Even though you never touched the boat, your hand's motion reached it through the water ripples.

Wireless chargers transfer electricity in a very similar way. Inside both the charging pad and your smartphone, there is a tightly wound spool of copper wire called a coil. When an electric current flows through the pad's coil, invisible ripples of a magnetic field form in the space right above it. Unlike water waves, however, these ripples only reach a tiny fraction of an inch away.

When the coil inside your phone catches these magnetic ripples, fresh electricity is created inside as if by magic. Even without metal prongs touching, the magnetic field acts as an invisible bridge to hand over power.

Thanks to this, we can easily charge our devices simply by resting them on a pad, without the hassle of fumbling to plug a cable into a tiny port.

Behind this phenomenon lies the law of electromagnetic induction, discovered by 19th-century scientist Michael Faraday. This physics principle states that when the strength or direction of a magnetic field rapidly changes around a conductor (a wire that carries electricity), electrical charges inside the wire are pushed into motion, creating a current on their own.

Instead of physically shaking a magnet back and forth, a charging pad sends an alternating current through its coil that reverses direction hundreds of thousands of times per second. As the current constantly flips, the surrounding magnetic field fluctuates violently.

The receiving coil inside your phone responds to this fluctuating magnetic field by generating electricity. Put more precisely, the pad is not tossing raw electricity across empty space; it triggers rapid shifts in the magnetic field that induce the phone to generate its own electricity.

This induced current is then converted and safely stored in your phone's battery.

If your phone slips even slightly off the center of a charging pad, charging can crawl to a halt or slow down dramatically. That is because inductive charging only transfers energy efficiently when the gap between the coils is tiny—just a few millimeters.

When the coils drift apart or their centers misalign, their magnetic coupling weakens and transfer efficiency drops. To push the same amount of power, the pad draws heavier current, which leads to greater energy loss and extra heat inside the coils, circuitry, and nearby metal parts.

This is exactly why modern smartphones feature circular magnets on their backs that snap firmly onto chargers. It is a clever trick to lock both coils into dead-center alignment, minimizing energy loss and heat buildup.

Moreover, if a stray piece of metal like a coin gets trapped between the pad and device, it can heat up dangerously. While many products—such as Qi-certified chargers—feature foreign object detection that cuts power automatically, not every charger has it. It is always wise to keep metal items away.