CBSE Class 11-science Answered

(i)  Hot reservoir supplies heat energy which is to be converted into work.

(ii)  Cold reservoir is that sub-system of the engine at lower temperature, where the part of the heat which has not been converted into work, is rejected.

(iii)  Working substance is that part which receives some heat (Q₁) from the hot substance (figure) and converts a part of it, i.e., (Q₁-Q₂) into work (W) and rejects the remaining Q₂ to the surroundings.

(iv)  The agents which transfer the energy from the engine to the external agents are mechanical parts. The cylinder with the piston, along with the crank-shaft, etc., are the mechanical parts.