What are Qi and Ki?

What you are seeing in the video clip are the Qi wireless power transfer logo and the charging location in a car. Many of the new cars have this facility and so does some of the mobile (cell phones) available in the market. That is a way of charging without plugging in a charger while you are travelling. Qi and Ki are wireless power transfer standards developed by the Wireless Power Consortium. Qi is for charging mobile devices like smartphones. Ki is a higher power standard for delivering cordless power for kitchen appliances. Principle of power transfer in both cases is by magnetic induction. Qi can handle up to 15W power for the Extended Power Profile. Ki meant for kitchen appliances can handle much higher power, even up to 2200W. Baseline Power Profile for smartphone like devices can give only up to 5W of wireless charging.

Wireless power transfer is not a new concept, though practical implementation has been delayed quite long after the initial invention by Nikola Tesla in early 20th century. This picture shows an incandescent light powered by electromagnetic induction. The large cylindrical component at the lower part of the picture is an electromagnet using a coil of wire and fed by an alternating current. Alternating magnetic field produced by it induces a current in the second coil held above it and connected to the bulb. This is one of the ways of wireless power transfer by near field inductive coupling. There are methods of capacitive coupling with electric fields and far field radiative coupling. Radiative coupling usually has low power transfer efficiency because only a small fraction of the radiated power is received by the receiving device.