By which one of the following working temperature the efficiency of a carnot engine obtained maximum ?

By which one of the following working temperature the efficiency of a

1.	By which one of the following working temperature the efficiency of a carnot engine obtained maximum ?
Answer» 100 K , 80 K 80 K , 60 K 40 K , 20 K 60 K , 40 K Solution :Efficiency of carnot engine `eta=1-T_2/T_1` `therefore` For getting maximum efficiency , the ratio of `T_2/T_1` MUST be minimum . From option (A) `T_2/T_1=80/100`=0.8 From option (B) `T_2/T_1=60/80=3/4`=0.75 From option (C) `T_2/T_1=20/40=1/2`=0.50 From option (D) `T_2/T_1=40/60 =2/3`=0.67 `therefore` The minimum value of `T_2/T_1` is in (C ) so efficiency obtained maximum