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<h2> Solutions of Savchenko Physics Textbook</h2>
<h2> Solutions of Savchenko Physics Textbook</h2>
<p class="author">
<p class="author">
Aliaksandr Melnichenka <br/>
Aliaksandr Melnichenka <br/>
October 2023
October 2023
</p>
</p>
</header>
</header>
<main >
<h3 id="back-link"><a href="../"> $ \leftarrow $ Back</a></h3>
<article >
<h3 id="back-link"><a href="../"> $ \leftarrow $ Back</a></h3>
<h3> Statement </h3>
<h4> Statement</h4>
<p >
<p>
$ 5.9.10^* $
$ 5.9.10^* $
Find the efficience of cycles shown in following figures, if as power agent it is taken a monoatomic ideal gas.
Find the efficience of cycles shown in following figures, if as power agent it is taken a monoatomic ideal gas.
</p >
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<center>
<figure>
<figure>
<img src="statement.png"
<img src="statement.png"
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<h 4 > Solution</h 4 >
<p class="TxtSolutions" >
<h 3 > Solution</h 3 >
a) Let enumerate the states from 1 to 4 in clockwise sense starting in the coordinate $ (P_1,V_1) $ . The efficience is defined as
<p>
</p>
a) Let enumerate the states from 1 to 4 in clockwise sense starting in the coordinate $ (P_1,V_1) $ . The efficience is defined as
<center>
$$ \eta = 1- \frac { |Q_c| }{ Q_h } =1- \frac { |Q_ { 34 } | }{ Q_ { 12 }} \;(1) $ $
$ \eta = 1- \frac { |Q_c| }{ Q_h } =1- \frac { |Q_ { 34 } | }{ Q_ { 12 }} \;(1) $
where $ Q_ { 34 } $ is the heat released by gas (cold reservoir) and $ Q_ { 12 } $ is the heat absorbed by gas (hot reservoir), while $ Q_ { 23 } $ and $ Q_ { 41 } $ are zero (adiabatic processes). Since $ 3-4 $ is an isochoric process,
</center>
$$ Q_ { 34 } = \Delta U_ { 34 } = nC_v \left (T_4-T_3 \right ) \;(2) $ $
<p class="TxtSolutions">
where $ Q_ { 34 } $ is the heat released by gas (cold reservoir) and $ Q_ { 12 } $ is the heat absorbed by gas (hot reservoir), while $ Q_ { 23 } $ and $ Q_ { 41 } $ are zero (adiabatic processes). Since $ 3-4 $ is an isochoric process,
</p>
<center>
$ Q_ { 34 } = \Delta U_ { 34 } = nC_v \left (T_4-T_3 \right ) \;(2) $
</center>
<p class="TxtSolutions">
From Poisson Law
From Poisson Law
</p>
$$ P_1V_1^ \gamma = P_4V_2^ \gamma $ $
<center>
$ P_1V_1^ \gamma = P_4V_2^ \gamma $
</center>
<p class="TxtSolutions">
and the state 4 is characterized by
and the state 4 is characterized by
</p>
$$ P_4V_2=nRT_4 $$
<center>
$ P_4V_2=nRT_4 $
</center>
<p class="TxtSolutions">
So, separating $ P_4 $ and putting it into above Poisson law
So, separating $ P_4 $ and putting it into above Poisson law
</p>
$ $ T_4 = \frac { P_1V_1^ \gamma }{ nRV_2^ { \gamma -1 }} \;(3) $ $
<center>
$ T_4 = \frac { P_1V_1^ \gamma }{ nRV_2^ { \gamma -1 }} \;(3) $
</center>
<p class="TxtSolutions">
Proceeding similarly, $ T_3 $ can be found. Applying Poisson Law for process $ 2-3 $ ,
Proceeding similarly, $ T_3 $ can be found. Applying Poisson Law for process $ 2-3 $ ,
</p>
$$ P_2V_1^ \gamma =P_3V_2^ \gamma $$
<center>
$ P_2V_1^ \gamma =P_3V_2^ \gamma $
</center>
<p class="TxtSolutions">
State equation for state 3 is
State equation for state 3 is
</p>
$$ P_3V_2=nRT_3 $$
<center>
$ P_3V_2=nRT_3 $
</center>
<p class="TxtSolutions">
Separating $ P_3 $ and substituting into respective Poisson Law
Separating $ P_3 $ and substituting into respective Poisson Law
</p>
$ $ T_3 = \frac { P_2V_1^ \gamma }{ nRV_2^ { \gamma -1 }} \;(4) $ $
<center>
$ T_3 = \frac { P_2V_1^ \gamma }{ nRV_2^ { \gamma -1 }} \;(4) $
</center>
<p class="TxtSolutions">
Substituting $ (3) $ and $ (4) $ into $ (2) $ , and as $ C_v=iR/2 $
Substituting $ (3) $ and $ (4) $ into $ (2) $ , and as $ C_v=iR/2 $
</p>
$ $ Q_ { 34 } = \frac { i }{ 2 } \frac { V_1^ \gamma }{ V_2^ { \gamma -1 }} \left (P_1-P_2 \right ) \;(5) $ $
<center>
$ Q_ { 34 } = \frac { i }{ 2 } \frac { V_1^ \gamma }{ V_2^ { \gamma -1 }} \left (P_1-P_2 \right ) \;(5) $
</center>
<p class="TxtSolutions">
For the process $ 1-2 $
For the process $ 1-2 $
</p>
$$ Q_ { 12 } = \Delta U_ { 12 } = nC_v \left (T_2-T_1 \right ) $$
<center>
$ Q_ { 12 } = \Delta U_ { 12 } = nC_v \left (T_2-T_1 \right ) $
</center>
<p class="TxtSolutions">
Taking account the state equations for states 1 and 2, temperatures can be found,
Taking account the state equations for states 1 and 2, temperatures can be found,
</p>
$$ Q_ { 12 } =nC_v \left ( \frac { P_2V_1 }{ nR } - \frac { P_1V_1 }{ nR } \right ) $$
<center>
$$ Q_ { 12 } = \frac { i }{ 2 } V_1 \left (P_2-P_1 \right ) \;(6) $$
$ Q_ { 12 } =nC_v \left ( \frac { P_2V_1 }{ nR } - \frac { P_1V_1 }{ nR } \right ) $
</center>
<center>
$ Q_ { 12 } = \frac { i }{ 2 } V_1 \left (P_2-P_1 \right ) \;(6) $
</center>
<p class="TxtSolutions">
Putting $ (5) $ and $ (6) $ into $ (1) $
Putting $ (5) $ and $ (6) $ into $ (1) $
</p>
$$ \eta = 1- \left ( \frac { V_1 }{ V_2 } \right )^ { \gamma -1 } $$
<center>
$ \eta = 1- \left ( \frac { V_1 }{ V_2 } \right )^ { \gamma -1 } $
</center>
<p class="TxtSolutions">
Since $ \gamma =C_p/C_v=1+2/i $ and $ i=3 $ (monoatomic gas),
Since $ \gamma =C_p/C_v=1+2/i $ and $ i=3 $ (monoatomic gas),
</p>
$ $ \boxed { \eta = 1- \left ( \frac { V_1 }{ V_2 } \right )^ { \frac { 2 }{ 3 }}} $ $
<center>
$ \boxed { \eta = 1- \left ( \frac { V_1 }{ V_2 } \right )^ { \frac { 2 }{ 3 }}} $
</center>
<p class="TxtSolutions">
b) Let enumerate again the states following a clockwise way, this time starting in coordinate $ (P_1,T_1) $ . The efficience is
b) Let enumerate again the states following a clockwise way, this time starting in coordinate $ (P_1,T_1) $ . The efficience is
</p>
$$ \eta = 1- \frac { |Q_c| }{ Q_h } \;(I) $$
<center>
$ \eta = 1- \frac { |Q_c| }{ Q_h } \;(I) $
</center>
<p class="TxtSolutions">
For identifying correctly the reservoirs, let's see the following graph corresponding to the cycle in a $ P $ vs $ V $ plot.
For identifying correctly the reservoirs, let's see the following graph corresponding to the cycle in a $ P $ vs $ V $ plot.
</p>
</p>
<center>
<center>
@@ -145,113 +100,50 @@
</figcaption>
</figcaption>
</figure>
</figure>
</center>
</center>
<p class="TxtSolutions" >
<p>
The hot reservoir is defined as
The hot reservoir is defined as
</p>
$ $ Q_h = Q_ { 23 } + Q_ { 34 } \;(II) $ $
<center>
$ Q_h = Q_ { 23 } + Q_ { 34 } \;(II) $
</center>
<p class="TxtSolutions">
and cold one
and cold one
</p>
$$ Q_c = Q_ { 12 } + Q_ { 41 } \;(III) $$
<center>
$ Q_c = Q_ { 12 } + Q_ { 41 } \;(III) $
</center>
<p class="TxtSolutions">
Process $ 2-3 $ is isobaric, then
Process $ 2-3 $ is isobaric, then
</p>
$$ Q_ { 23 } =nC_p \left (T_2-T_1 \right ) \;(IV) $$
<center>
$ Q_ { 23 } =nC_p \left (T_2-T_1 \right ) \;(IV) $
</center>
<p class="TxtSolutions">
Process $ 3-4 $ is isothermal, so
Process $ 3-4 $ is isothermal, so
</p>
$ $ Q_ { 34 } = A_ { 34 } = nRT_2 \ln { \frac { V_4 }{ V_3 }} $ $
<center>
$ Q_ { 34 } = A_ { 34 } = nRT_2 \ln { \frac { V_4 }{ V_3 }} $
</center>
<p class="TxtSolutions">
Since $ V=nRT/P $ according state equation
Since $ V=nRT/P $ according state equation
</p>
$ $ Q_ { 34 } = nRT_2 \ln { \frac { P_2 }{ P_1 }} \;(V) $ $
<center>
$ Q_ { 34 } = nRT_2 \ln { \frac { P_2 }{ P_1 }} \;(V) $
</center>
<p class="TxtSolutions">
Substituting $ (IV) $ and $ (V) $ into $ (II) $ and taking account that $ C_p=(i+2)R/2 $
Substituting $ (IV) $ and $ (V) $ into $ (II) $ and taking account that $ C_p=(i+2)R/2 $
</p>
$ $ Q_h = \frac { i+2 }{ 2 } nR \left (T_2-T_1 \right )+nRT_2 \ln { \frac { P_2 }{ P_1 }} \;(VI) $ $
<center>
$ Q_h = \frac { i+2 }{ 2 } nR \left (T_2-T_1 \right )+nRT_2 \ln { \frac { P_2 }{ P_1 }} \;(VI) $
</center>
<p class="TxtSolutions">
Process $ 1-2 $ is isothermal, so
Process $ 1-2 $ is isothermal, so
</p>
$ $ Q_ { 12 } =A_ { 12 } =nRT_1 \ln { \frac { V_2 }{ V_1 }} $ $
<center>
$ Q_ { 12 } =A_ { 12 } =nRT_1 \ln { \frac { V_2 }{ V_1 }} $
</center>
<p class="TxtSolutions">
and newly, taking account state equation
and newly, taking account state equation
</p>
$ $ Q_ { 12 } =A_ { 12 } =nRT_1 \ln { \frac { P_1 }{ P_2 } \;(VII) } $ $
<center>
$ Q_ { 12 } =A_ { 12 } =nRT_1 \ln { \frac { P_1 }{ P_2 } \;(VII) } $
</center>
<p class="TxtSolutions">
Finally, process $ 4-1 $ is isobaric
Finally, process $ 4-1 $ is isobaric
</p>
$$ Q_ { 14 } = nC_p \left (T_1-T_2 \right ) \;(VIII) $$
<center>
$ Q_ { 14 } = nC_p \left (T_1-T_2 \right ) \;(VIII) $
</center>
<p class="TxtSolutions">
Substituting $ (VII) $ and $ (VIII) $ into $ (III) $
Substituting $ (VII) $ and $ (VIII) $ into $ (III) $
</p>
$ $ Q_c = nRT_1 \ln { \frac { P_1 }{ P_2 }} + \frac { i+2 }{ 2 } nR \left (T_1-T_2 \right ) \;(IX) $ $
<center>
$ Q_c = nRT_1 \ln { \frac { P_1 }{ P_2 }} + \frac { i+2 }{ 2 } nR \left (T_1-T_2 \right ) \;(IX) $
</center>
<p class="TxtSolutions">
Substituting $ (VI) $ and $ (IX) $ into $ (I) $ and developing algebraically
Substituting $ (VI) $ and $ (IX) $ into $ (I) $ and developing algebraically
</p>
$ $ \eta = \frac { 2 \left (T_2-T_1 \right ) \ln { \frac { P_2 }{ P_1 }}}{ (i+2) \left (T_2-T_1 \right )+2T_2 \ln { \frac { P_2 }{ P_1 }}} $ $
<center>
$ \eta = \frac { 2 \left (T_2-T_1 \right ) \ln { \frac { P_2 }{ P_1 }}}{ (i+2) \left (T_2-T_1 \right )+2T_2 \ln { \frac { P_2 }{ P_1 }}} $
</center>
<p class="TxtSolutions">
Since gas is monoatomic, $ i = 3 $ , hence
Since gas is monoatomic, $ i = 3 $ , hence
$$ \boxed { \eta = \frac { 2 \left (T_2-T_1 \right ) \ln { \frac { P_2 }{ P_1 }}}{ 5 \left (T_2-T_1 \right )+2T_2 \ln { \frac { P_2 }{ P_1 }}}} $$
</p>
</p>
<center>
$ \boxed { \eta = \frac { 2 \left (T_2-T_1 \right ) \ln { \frac { P_2 }{ P_1 }}}{ 5 \left (T_2-T_1 \right )+2T_2 \ln { \frac { P_2 }{ P_1 }}}} $
</center>
<p class="TxtSolutions" style="text-align: right; font-style: italic; font-size: 14;">
BSc. Luis Daniel Fernández Quintana<br>
Physics Department (FCNE)<br>
Universidad de Oriente, Cuba<br>
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