Bekele, Mulugeta (PhD)Getachew, Anteneh2018-06-182023-11-092018-06-182023-11-092007-07http://10.90.10.223:4000/handle/123456789/1382We analytically study a thermal Brownian motor and calculate exactly the Onsager's coe±cients in equilibrium and steady state conditions. We show that the reciprocity relation holds and the determinant of the Onsager's matrix vanishes. Such a condi- tion implies that the device is built with tight coupling. This tells us why Carnot's e±ciency can be achieved in the limit of in¯nitely slow velocities (quasistatic pro- cess). We also ¯nd the e±ciency and the coe±cient of performance for our model at these conditions using Onsager's coe±cients. The e±ciency and the coe±cient of performance that we found using the tools of LIT is exactly the same as the Carnot's e±ciency and coe±cient of performance. Also we ¯nd the e±ciency (at maximum power) and the maximum coe±cient of performance of the Brownian refrigerator to be exactly identical with the the corrosponding results of Curzon - Alhborn and Carnot's refrgerator for perfectly tight coupling modelenLinear Irreversible ThermodynamicsThesis