A Unified Model of Magnetic Extraction of Spin Energy from aBlack Hole

A unified model of magnetic extraction of spin energy from a black hole is discussed based on the theory of black hole magnetosphere. The magnetic extracting power is expressed by a unified formular, which is applicable to both the Blandford-Znajek (BZ) process and the magnetic coupling (MC) process. Strength and characteristics of the BZ power and the MC power are compared detailedly. In addition, the impedance matching condition for the BZ power is extended to the more general case.