Acad Sinica, Inst High Energy Phys, Beijing 100039, Peoples R China
; Zhengzhou Univ, Dept Phys, Zhengzhou 450052, Peoples R China
The motion of a heavily damped Brownian particle which has an internal degree of freedom is considered. Directed motion of the Brownian particle is generated by external action which acts only on the internal degree of freedom. For a simple case that the internal degree of freedom is rotated continuously, the current is evaluated explicitly. (C) 1998 Elsevier Science B.V. All rights reserved.