• # question_answer In a fluid coupling, the torque transmitted is 50 kN.m, when the speed of the driving and driven shaft is 900 rpm and 720 rpm respectively. The efficiency of the fluid coupling will be: A) 20%                             B) 25%C) 80%                             D) 90%.

Efficiency of hydraulic coupling $\cos \alpha =\frac{1}{2},$ $\alpha =60{}^\circ$ $\frac{{{N}_{2}}}{{{N}_{2}}}=\frac{720}{900}=0.8\,\,or\,\,80%$