English: A generic block diagram of a wireless power system. "Wireless power transfer" is a collective term for several different technologies which transfer power across space without wires using electromagnetic fields. A wireless power system consists of a "transmitter" device connected to a power supply such as mains power line, which converts energy to a time varying electromagnetic field, which transmits the energy across an intervening space to a "receiver" device, which converts it back to an electric current which powers a load.