Elecrical engineering. Electrical energy is transferred through alternating magnetic fields from a charging station to the device to be charged. This technology is commonly used for electric toothbrushes and is now rising in the areas of smartphones and electric vehicles.
The Inductive Power Transfer (IPT) uses a primary coil to generate an oscillating magnetic field at the charging station. This field runs through a secondary coil at the device to be charged and induces an alternating current which can be used with a rectifier to recharge a battery.
The Magnetic Resonance Coupling (MRC) is an extension of the inductive power transfer with additional resonant oscillation circuits in between the coils. The effect is a higher efficiency factor and a higher range but in cost of a lower power limit.
Known technologies and standards are Qi, Powermat, Rezence and WiTricity.