The efficiency of a Carnot engine working between the source at absolute temperature T1 and the sink at an absolute temperature T2 is
`((T_1 - T_2)/T_1 - 1) xx 100`
`(1 - T_2/T_1) xx 100`
`1/(T_1 T_2 xx 100)`
`(T_2 - T_1)/T_1 xx 100`
what is carnot engine and how does this work? what are its uses?