Answer :

The steam engine absorbs energy in form of heat from boiler and converts some of it into mechanical work and return rest to the surrounding or we can say some part of heat absorbed is converted into work and rest is wasted, suppose Q1 heat is absorbed from Boiler (Source), W amount of work is done by the engine and Q2 heat is returned to the surroundings (Sink)


As has been shown diagrammatically



So we have


Q1 = W + Q2


Now since engine is absorbing 3.6 × 109J of heat per minute from its boiler so each minute amount of heat absorbed by engine from Boiler is


Q1 = 3.6 × 109J


steam engine delivers 5.4×108J of work per minute, so each minute work done by engine is


W = 5.4×108J


Now efficiency is defined as the amount of work done per unit supplies Energy , or it is the ratio of work output and the heat input of the system , mathematically



Where W is the work done by engine and Q1 is the amount heat absorbed


So efficiency of the engine is



In percentage form



So the efficiency of the engine is 15%


Now we need to find the amount of heat wasted, which is the amount of heat or energy transferred back to Surrounding (Sink) without doing any work, denoted by Q2


We already know


Q1 = W + Q2


Or we can say


Q2 = Q1 – W


Now since engine is absorbing 3.6 × 109J of heat per minute from its boiler so each minute amount of heat absorbed by engine from Boiler is


Q1 = 3.6 × 109J


steam engine delivers 5.4×108J of work per minute, so each minute work done by engine is


W = 5.4×108J


So we get


Q2 = 3.6 × 109J 5.4 × 108J


= 36 × 108 J - 5.4 × 108J = 30.6 × 108J


=3.06 ×109 J


i.e. 3.06 ×109 J of heat is wasted each minute or we can say


3.06 ×109 J heat per minute is being wasted


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