ELI5 - How do wireless phone chargers work?

A wireless phone charger feels a bit like magic, but it is really just smart use of electricity and magnets.

Inside the charging pad is a flat copper coil. Inside your phone is another flat copper coil. These coils are very close to each other when you place your phone on the pad. They do not touch, but that is okay. When you plug the charger into the wall, electricity flows into the coil inside the pad. This electricity moves back and forth very fast. When electricity moves like that, it creates an invisible magnetic field around the coil. You cannot see it, but it is there.

That magnetic field spreads a short distance above the charger. When your phone is sitting on the pad, the magnetic field reaches the coil inside your phone. The moving magnetic field makes electricity start moving inside the phone’s coil. This is called electromagnetic induction, but you can think of it as electricity jumping across the tiny gap using magnet power. The electricity created in the phone’s coil is then sent to the phone’s battery. The battery stores that energy, just like it does when you use a normal cable. The phone’s software controls the process so the battery fills safely and does not overheat.

Wireless chargers only work at very short distances. If the phone is too far away, the magnetic field becomes too weak. That is why you usually have to place the phone directly on the pad and sometimes line it up just right. If the coils are not lined up well, charging can be slow or stop completely. Wireless charging is usually slower than charging with a cable. Some energy is lost as heat because the magnetic field is not perfectly efficient. That is why phones can feel warm while charging wirelessly. Newer chargers try to reduce this loss, but some waste is normal.

There is also a common standard called Qi. This is like a shared language. It lets phones and chargers from different brands work together. If your phone supports Qi, it can charge on most wireless pads. So in simple terms, a wireless charger sends energy through the air using a magnetic field. Your phone catches that energy with a coil inside it. The battery stores it. No plugs needed. Just place, wait, and charge.