<p>PHYSICS ESSAYS ( Volume 25, Issue 2 (June 2012) ) P172~176</p> <p>URL: http://physicsessays.org/toc/phes/25/2</p> <p>Entropy: A concept that is not a physical quantity</p> <p>Shufeng-zhang</p> <p>College of Physics, Central South University, 932 Lushan south Road, Changsha 410083, China</p> <p>E-mail: uhsgnahz@126.com</p> <p>Abstract : This study has demonstrated that entropy is not a physical quantity, that is, the physical quantity called entropy does not exist. If the efficiency of heat engine is defined as η = W/W1, and the reversible cycle is considered to be the Stirling cycle, then, given ∮dQ/T = 0, we can prove ∮dW/T = 0 and ∮d/T = 0. If ∮dQ/T = 0, ∮dW/T = 0 and ∮dE/T = 0 are thought to define new system state variables, such def...