A Carnot's engine whose sink is at temperature of 300K has an efficiency of `40%` By how much should the temperature of the source be increased so as to increase the efficiency to 60%?

Explanation

`(T_(2))/(T_(1))=1-eta=1-(40)/(100)=(3)/(5)`
`rArrT_(1)=(5)/(3)T_(2)rArrT_(1)=(5)/(3)xx300=500K`
New efficiency `eta=60%`
`(T_(2))/(T_(1))=1-eta'=1-(60)/(100)=(2)/(5)`
`T_(1)'=(5)/(2)xx300=750K: DeltaT=750-500=250K`