ANS:C - 66.6

The efficiency of power transmission through a circular pipe is given by: η=ht−hfht×100%\eta = \frac{h_t - h_f}{h_t} \times 100\%η=ht​ht​−hf​​×100% where:

• hth_tht​ is the total head at the inlet of the pipe,
• hfh_fhf​ is the head loss due to friction along the length of the pipe.

To find the maximum efficiency, we need to understand that hfh_fhf​ represents the head loss due to friction, which is related to the length of the pipe, the flow rate, and the roughness of the pipe walls. The maximum efficiency is achieved when hfh_fhf​ is minimized, ideally approaching zero. Given the choices:

• 33.3% (approximately) corresponds to the scenario where the head loss due to friction hfh_fhf​ is minimized, resulting in the highest possible efficiency of power transmission through the pipe.

Therefore, the correct answer is 33.3%. This value represents the maximum efficiency achievable under ideal conditions of minimal friction losses in the pipe.