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Grade 12Mechanics

a steam engine delivers 7.5x10*8J of work per minute and services 3.6x10*9J of heat per minute from its boiler . what is the efficiencyof the engine ?how much hea is wasted per minute ? also find the ratio of temperature of sink to the souce

Profile image of MOHAMMED K HISHAM
8 Years agoGrade 12
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1 Answer

Profile image of Askiitians Tutor Team
ApprovedApproved Tutor Answer1 Year ago

To determine the efficiency of the steam engine, the amount of work it produces, the heat it receives, and the heat wasted must be analyzed. Let's break this down step by step.

Calculating Efficiency

The efficiency of an engine can be calculated using the formula:

Efficiency (η) = (Work Output / Heat Input) × 100%

In this case, the work output is given as:

Work Output = 7.5 × 108 J/min

The heat input from the boiler is:

Heat Input = 3.6 × 109 J/min

Now, substituting these values into the efficiency formula:

Efficiency (η) = (7.5 × 108 J/min) / (3.6 × 109 J/min) × 100%

Calculating this gives:

η = (7.5 / 36) × 100% = 20.83%

Heat Wasted Calculation

To find out how much heat is wasted per minute, we can use the following relationship:

Heat Wasted = Heat Input - Work Output

Substituting the known values:

Heat Wasted = 3.6 × 109 J/min - 7.5 × 108 J/min

Calculating this gives:

Heat Wasted = 3.6 × 109 J/min - 0.75 × 109 J/min = 2.85 × 109 J/min

Finding the Temperature Ratio

To find the ratio of the temperatures of the sink (Tsink) to the source (Tsource

Efficiency (η) = 1 - (Tsink / Tsource)

Rearranging this gives:

Tsink / Tsource = 1 - η

Substituting the efficiency we calculated:

Tsink / Tsource = 1 - 0.2083 = 0.7917

This means that the ratio of the temperature of the sink to the source is approximately:

0.7917

Summary of Findings

  • Efficiency of the engine: 20.83%
  • Heat wasted per minute: 2.85 × 109 J/min
  • Temperature ratio (Tsink / Tsource): 0.7917

This analysis shows how we can derive important performance metrics for a steam engine, illustrating the principles of thermodynamics in action.