Questions: Problem 2: (9% of Assignment Value)
In this problem a heat engine, each cycle, absorbs an amount of energy Qh=1780 J from a hot reservoir and expels an amount Qc=1310 J into a cold reservoir. Each cycle lasts for a time of t=0.23 seconds.
Part (a)
Find the efficiency of an ideal engine operating between these reservoirs. Remember the efficiency is unit-less, therefore so should your number be.
eideal =
Transcript text: Problem 2: (9\% of Assignment Value)
In this problem a heat engine, each cycle, absorbs an amount of energy $Q_{h}=1780 \mathrm{~J}$ from a hot reservoir and expels an amount $Q_{c}=1310 \mathrm{~J}$ into a cold reservoir. Each cycle lasts for a time of $t=0.23$ seconds.
Part (a)
Find the efficiency of an ideal engine operating between these reservoirs. Remember the efficiency is unit-less, therefore so should your number be as well.
\[
e_{\text {ideal }}=\square
\]
Solution
Solution Steps
Step 1: Understand the Problem
We are given a heat engine that absorbs energy \( Q_h = 1780 \, \text{J} \) from a hot reservoir and expels energy \( Q_c = 1310 \, \text{J} \) to a cold reservoir. We need to find the efficiency of this engine.
Step 2: Recall the Formula for Efficiency
The efficiency \( e \) of a heat engine is given by the formula:
\[
e = \frac{W}{Q_h}
\]
where \( W \) is the work done by the engine. The work done can be calculated as the difference between the heat absorbed and the heat expelled:
\[
W = Q_h - Q_c
\]
Step 3: Calculate the Work Done
Substitute the given values into the formula for work:
\[
W = 1780 \, \text{J} - 1310 \, \text{J} = 470 \, \text{J}
\]
Step 4: Calculate the Efficiency
Now, substitute the values of \( W \) and \( Q_h \) into the efficiency formula:
\[
e = \frac{470 \, \text{J}}{1780 \, \text{J}}
\]
Step 5: Simplify the Efficiency Expression
Calculate the efficiency:
\[
e = \frac{470}{1780} \approx 0.2640
\]
Final Answer
The efficiency of the engine is \(\boxed{0.2640}\).