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electrical_engineering_and_electronics_1:block06 [2025/09/29 00:23] – angelegt mexleadmin | electrical_engineering_and_electronics_1:block06 [2025/09/29 00:57] (aktuell) – mexleadmin |
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<WRAP> <imgcaption imageNob7 | Resistance of linear sources> </imgcaption> \\ {{url>https://www.falstad.com/circuit/circuitjs.html?running=false&ctz=CQAgDOB0YzCsICMZICYaoOyYMxgByoBsAnCZkiAgCw5UCmAtIogFABuIJRIqcP3JJh4QI1CAlFQ4rAE5ceiYUMXKIyGKwDuC3vxV6RrVIh6pU1Q7wsH1265b6qz+sPaXOHt1gEsQOdCsA9TUoeHtggxx8Sw9wOX8YqKSncCRYCJT9SNS3HWjY5WoiQqN8rJ5ix1djUxAqqwa4uwBzL1TzR3x8NLc2htSB7t7WACMQIkQkOFiiOixUePHUcmme6hZeTEW3AA9eElicGjgexGj6pB6AGx8AO3oAQ1kAHQBnAGMAV1lZejuAC7vN4Aex+H3orH2JSQODMeFhJEuiBu9yerze7BB1wBjxa9GBYNkENYQA noborder}} </WRAP> | <WRAP> <imgcaption imageNob7 | Resistance of linear sources> </imgcaption> \\ {{url>https://www.falstad.com/circuit/circuitjs.html?running=false&ctz=CQAgDOB0YzCsICMZICYaoOyYMxgByoBsAnCZkiAgCw5UCmAtIogFABuIJRIqcP3JJh4QI1CAlFQ4rAE5ceiYUMXKIyGKwDuC3vxV6RrVIh6pU1Q7wsH1265b6qz+sPaXOHt1gEsQOdCsA9TUoeHtggxx8Sw9wOX8YqKSncCRYCJT9SNS3HWjY5WoiQqN8rJ5ix1djUxAqqwa4uwBzL1TzR3x8NLc2htSB7t7WACMQIkQkOFiiOixUePHUcmme6hZeTEW3AA9eElicGjgexGj6pB6AGx8AO3oAQ1kAHQBnAGMAV1lZejuAC7vN4Aex+H3orH2JSQODMeFhJEuiBu9yerze7BB1wBjxa9GBYNkENYQA noborder}} </WRAP> |
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In the simulation, a measuring current $I_\Omega$ is used to determine the resistance value. ((This concept will also be used in an electrical engineering lab experiment on [[elektrotechnik_labor:1_widerstaende|resistor]]s in the 3rd semester.)) Let us have a look at the properties of the ohmmeter in the simulation by double-clicking on the ohmmeter. Here, a very large measuring current of $I_\Omega=1~\rm A$ is used. This could lead to high voltages or the destruction of components in real setups. \\ | In the simulation, a measuring current $I_\Omega$ is used to determine the resistance value. ((This concept will also be used in an electrical engineering lab experiment on [[elektrotechnik_labor:1_widerstaende|resistor]]s in the 2nd semester.)) Let us have a look at the properties of the ohmmeter in the simulation by double-clicking on the ohmmeter. Here, a very large measuring current of $I_\Omega=1~\rm A$ is used. This could lead to high voltages or the destruction of components in real setups. \\ |
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In order to understand why is this nevertheless chosen so high in the simulation, do the following: Set the measuring current for both linear sources to (more realistic) $1~\rm mA$. What do you notice? | In order to understand why is this nevertheless chosen so high in the simulation, do the following: Set the measuring current for both linear sources to (more realistic) $1~\rm mA$. What do you notice? |
<WRAP> <imgcaption imageNo8 | circuit with two current sources> </imgcaption> {{drawio>SchaltungZeiStromquellen.svg}} </WRAP> | <WRAP> <imgcaption imageNo8 | circuit with two current sources> </imgcaption> {{drawio>SchaltungZeiStromquellen.svg}} </WRAP> |
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<callout icon="fa fa-exclamation" color="red" title="Note:"> If resistors are to be measured in a circuit, at least one terminal of the resistor must be disconnected from the circuit. Otherwise, other sources or resistors may falsify the measurement result. </callout> | Any interconnection of __linear__ voltage sources, current sources, and __ohmic__ resistors can be seen as |
| * as a single, linear voltage source \\ ({{https://en.wikipedia.org/wiki/Thévenin_theorem|Thévenin theorem}} ) or |
| * as a single, linear current source \\ ({{https://en.wikipedia.org/wiki/Norton_theorem|Norton theorem}} ) |
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| In <imgref imageNo63 > it can be seen that the three circuits give the same result (voltage/current) with the same load. This is also true when an (AC) source is used instead of the load. |
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| <WRAP> <imgcaption imageNo63 | Equivalent voltage and current source> </imgcaption> \\ {{url>https://www.falstad.com/circuit/circuitjs.html?running=false&ctz=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-sd7jMEdzhfLyKr1MkZGGcTBuh4MCwYhodcYjQcBcgoNAUAoMAGAPAAlAB9AAZOlWDfXQP1EL9wHMSU2U4ABlPh4mkFDiEOToQAAM27YdmHRQCSLoVhSF0Gw+GIOgGxABDFw7AATej3hQJioFYSg2K8TjuL4l13EqHc2lMGTP3QtCSlCag5KI51-FQmMSNyL8XVQsJ9IUtTfBM3xDNtRI9JCayQzMvTDIItNGN8N5KOo2iLGQ+zRBMzCoJWHCBXoogQN0YDIOg554KQ6J2ESYMY0wn8-wA1xcQsZ4wm9LFVNxAJ+myDlUu5YqZAIhkYyKvKsKorsaLonQivkMr5HIkL+VOQDVCYUZ3noTj4q4LVcq5TomnS-9shqsI5Ly7JFo0xV8rKsJhhjdaKqDbkloAI0Iyo6n4PAoCCRSjv4YUQDqMAmEumRrowUi+CQLx+ECDxnWuyDciQKDgOYzRy2FITiGCNBcmYySeP4xcGGCI40GA39VFQaAiSUbpDybWALyvWAlxXNdEbArCOOgVHwFgDG4CxrDd2Aphm1gcdJ2Jp8X0Ri6UbRum1ngCCyhAKAmAolsuy7EdRzDZ8237TggA noborder}} </WRAP> |
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| ~~PAGEBREAK~~ ~~CLEARFIX~~ |
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<panel type="info" title="Example / micro-exercise"> | <panel type="info" title="Example / micro-exercise"> |
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~~PAGEBREAK~~ ~~CLEARFIX~~ | ~~PAGEBREAK~~ ~~CLEARFIX~~ |
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Any interconnection of __linear__ voltage sources, current sources, and __ohmic__ resistors can be. | |
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* as a single, linear voltage source \\ ({{https://en.wikipedia.org/wiki/Thévenin_theorem|Thévenin theorem}} ) or | |
* as a single, linear current source \\ ({{https://en.wikipedia.org/wiki/Norton_theorem|Norton theorem}} ) | |
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In <imgref imageNo63 > it can be seen that the three circuits give the same result (voltage/current) with the same load. This is also true when an (AC) source is used instead of the load. | |
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<WRAP> <imgcaption imageNo63 | Equivalent voltage and current source> </imgcaption> \\ {{url>https://www.falstad.com/circuit/circuitjs.html?running=false&ctz=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-sd7jMEdzhfLyKr1MkZGGcTBuh4MCwYhodcYjQcBcgoNAUAoMAGAPAAlAB9AAZOlWDfXQP1EL9wHMSU2U4ABlPh4mkFDiEOToQAAM27YdmHRQCSLoVhSF0Gw+GIOgGxABDFw7AATej3hQJioFYSg2K8TjuL4l13EqHc2lMGTP3QtCSlCag5KI51-FQmMSNyL8XVQsJ9IUtTfBM3xDNtRI9JCayQzMvTDIItNGN8N5KOo2iLGQ+zRBMzCoJWHCBXoogQN0YDIOg554KQ6J2ESYMY0wn8-wA1xcQsZ4wm9LFVNxAJ+myDlUu5YqZAIhkYyKvKsKorsaLonQivkMr5HIkL+VOQDVCYUZ3noTj4q4LVcq5TomnS-9shqsI5Ly7JFo0xV8rKsJhhjdaKqDbkloAI0Iyo6n4PAoCCRSjv4YUQDqMAmEumRrowUi+CQLx+ECDxnWuyDciQKDgOYzRy2FITiGCNBcmYySeP4xcGGCI40GA39VFQaAiSUbpDybWALyvWAlxXNdEbArCOOgVHwFgDG4CxrDd2Aphm1gcdJ2Jp8X0Ri6UbRum1ngCCyhAKAmAolsuy7EdRzDZ8237TggA noborder}} </WRAP> | |
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~~PAGEBREAK~~ ~~CLEARFIX~~ | |
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==== Simplified Determination of the internal Resistance ==== | ==== Simplified Determination of the internal Resistance ==== |
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===== Exercises ===== | ===== Exercises ===== |
~~PAGEBREAK~~ ~~CLEARFIX~~ | ~~PAGEBREAK~~ ~~CLEARFIX~~ |
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<panel type="info" title="Exercise 3.2.1 Solving a circuit simplification I"> <WRAP group><WRAP column 2%>{{fa>pencil?32}}</WRAP><WRAP column 92%> | |
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{{youtube>xtOPwmUgPjc}} | |
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</WRAP></WRAP></panel> | |
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<panel type="info" title="Exercise 3.2.2 Solving a circuit simplification II"> <WRAP group><WRAP column 2%>{{fa>pencil?32}}</WRAP><WRAP column 92%> | |
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{{youtube>UU_RJJ6ne4I}} | |
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</WRAP></WRAP></panel> | |
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<panel type="info" title="Exercise 3.2.3 Solution sketch for a more difficult circuit simplification"> <WRAP group><WRAP column 2%>{{fa>pencil?32}}</WRAP><WRAP column 92%> | |
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{{youtube>In3NF8f-mzg}} | |
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</WRAP></WRAP></panel> | |
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<panel type="info" title="Exercise 3.2.4 Interesting circuit tasks"> <WRAP group><WRAP column 2%>{{fa>pencil?32}}</WRAP><WRAP column 92%> | |
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{{youtube>zTDgziJC-q8}} | |
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</WRAP></WRAP></panel> | |
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<panel type="info" title="Exercise 3.1.1 Convert current source to voltage source"> <WRAP group><WRAP column 2%>{{fa>pencil?32}}</WRAP><WRAP column 92%> | |
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{{youtube>ZqohGL-40a4}} | |
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</WRAP></WRAP></panel> | |
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<panel type="info" title="Exercise 3.1.2 Convert voltage source to current source"> <WRAP group><WRAP column 2%>{{fa>pencil?32}}</WRAP><WRAP column 92%> | |
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{{youtube>vVDNsztDmAk}} | |
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</WRAP></WRAP></panel> | |
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{{page>task_3.1.3_with_calculation&nofooter}} | |
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~~PAGEBREAK~~ ~~CLEARFIX~~ | |
===== Common pitfalls ===== | |
* **Wrong deactivation:** do **not** set an ideal voltage source to open or an ideal current source to short; the rules are: $U$-source→**short**, $I$-source→**open**. | |
* **Confusing goals:** **max power** ($R_{\rm L}=R_{\rm i}$, $\eta=50\%$) vs. **high efficiency** ($R_{\rm L}\gg R_{\rm i}$). Don’t equate them. | |
* **Ignoring ratings:** not every real source is short-circuit-proof—$I_{\rm SC}$ is a **model parameter**, not a recommended experiment. | |
* **Mixed conventions:** keep the **passive sign convention** for loads; use conventional current ($+$ to $-$). | |
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===== Exercises ===== | |
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==== Quick checks ==== | ==== Quick checks ==== |
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#@TaskTitle_HTML@##@Lvl_HTML@#~~#@ee1_taskctr#~~.1 From $U_{\rm OC}$, $I_{\rm SC}$ to $R_{\rm i}$ and $U_{\rm L}$ | |
#@TaskText_HTML@# | |
A source has $U_{\rm OC}=12.0~\rm V$, $I_{\rm SC}=3.0~\rm A$. Find $R_{\rm i}$ and, for $R_{\rm L}=9.0~\Omega$, compute $U_{\rm L}$ and $\eta$. | |
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#@ResultBegin_HTML~Exercise1~@# | |
$R_{\rm i}=U_{\rm OC}/I_{\rm SC}=4.00~\Omega$. | |
$U_{\rm L}=U_{\rm OC}\dfrac{R_{\rm L}}{R_{\rm L}+R_{\rm i}}=12.0~{\rm V}\cdot \dfrac{9.0~\Omega}{13.0~\Omega}=8.31~{\rm V}$. | |
$\eta=\dfrac{R_{\rm L}}{R_{\rm L}+R_{\rm i}}=\dfrac{9.0}{13.0}=0.692\;(-)$. | |
#@ResultEnd_HTML@# | |
#@TaskEnd_HTML@# | |
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#@TaskTitle_HTML@##@Lvl_HTML@#~~#@ee1_taskctr#~~.2 Thevenin ↔ Norton conversion | #@TaskTitle_HTML@##@Lvl_HTML@#~~#@ee1_taskctr#~~.2 Thevenin ↔ Norton conversion |
#@ResultEnd_HTML@# | #@ResultEnd_HTML@# |
#@TaskEnd_HTML@# | #@TaskEnd_HTML@# |
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==== Longer exercises ==== | ==== Longer exercises ==== |
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#@TaskTitle_HTML@##@Lvl_HTML@#~~#@ee1_taskctr#~~.1 Loaded divider as Thevenin | |
#@TaskText_HTML@# | |
A divider $R_1=3.3~\rm k\Omega$, $R_2=6.8~\rm k\Omega$ is fed from $U=10.0~\rm V$ and loaded by $R_{\rm L}=10.0~\rm k\Omega$. Replace the divider by its Thevenin equivalent, then compute $U_{\rm L}$ and the **loading error** relative to the ideal (no-load) divider output. | |
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#@ResultBegin_HTML~LongerExercise1~@# | |
$R_{\rm ie}=R_1\parallel R_2=\dfrac{(3.3)(6.8)}{3.3+6.8}~\rm k\Omega=2.22~\rm k\Omega$. | |
$U_{0\rm e}=\dfrac{R_2}{R_1+R_2}U=6.8/(3.3+6.8)\cdot 10.0~\rm V=6.80~\rm V$. | |
$U_{\rm L}=U_{0\rm e}\dfrac{R_{\rm L}}{R_{\rm L}+R_{\rm ie}}=6.80~{\rm V}\cdot \dfrac{10.0}{12.22}=5.56~{\rm V}$. | |
Ideal (no-load) output would be $6.80~\rm V$ ⇒ loading error $=1.24~\rm V$. | |
#@ResultEnd_HTML@# | |
#@TaskEnd_HTML@# | |
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<panel type="info" title="Exercise 3.1.1 Convert current source to voltage source"> <WRAP group><WRAP column 2%>{{fa>pencil?32}}</WRAP><WRAP column 92%> | <panel type="info" title="Exercise 3.1.1 Convert current source to voltage source"> <WRAP group><WRAP column 2%>{{fa>pencil?32}}</WRAP><WRAP column 92%> |
</WRAP></WRAP></panel> | </WRAP></WRAP></panel> |
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~~PAGEBREAK~~ ~~CLEARFIX~~ | |
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===== Embedded resources ===== | <panel type="info" title="Exercise 3.3.1 Simplification by Norton / Thevenin theorem"> <WRAP group><WRAP column 2%>{{fa>pencil?32}}</WRAP><WRAP column 92%> <WRAP> |
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<WRAP> DC Voltage & Current Source Theory | Simplify the following circuits by the Norton theorem to a linear current source (circuits marked with NT) or by Thevenin theorem to a linear voltage source (marked with TT). |
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{{youtube>AQK7RyecVW0}} | <imgcaption BildNr3_0 | Simplification by Norton / Thevenin theorem> </imgcaption> {{drawio>BildNr3_0.svg}} </WRAP> |
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</WRAP> | <button size="xs" type="link" collapse="Loesung_3_3_1_1_Lösungsweg">{{icon>eye}} Solution</button><collapse id="Loesung_3_3_1_1_Lösungsweg" collapsed="true"> |
| To substitute the circuit in $a)$ first we determine the inner resistance. |
| Shutting down all sources leads to |
| \begin{equation*} |
| R_{\rm i}= 8~\Omega \end{equation*} |
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| Next, we figure out the current in the short circuit. |
| In case of a short circuit, we have $2~V$ in a branch which in turn means there must be $−2~V$ on the resistor. |
| The current through that branch is |
| \begin{equation*} I_R=\frac{2~V}{8~\Omega} \end{equation*} |
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| The current in question is the sum of both the other branches |
| \begin{equation*} I_S= I_R + 1~A \end{equation*} |
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| To substitute the circuit in $b)$ first we determine the inner resistance. |
| Shutting down all sources leads to |
| \begin{equation*} R_{\rm i}= 4 ~\Omega \end{equation*} |
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| Next, we figure out the voltage at the open circuit. |
| Thus we know the given current flows through the ideal current source as well as the resistor. |
| The voltage drop on the resistor is |
| \begin{equation*} R_{\rm i}= -4~\Omega \cdot 2~A \end{equation*} |
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| The voltage at the open circuit is |
| \begin{equation*} U_{\rm S}= 2~V + 1~V + U_R \end{equation*} |
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| </collapse> <button size="xs" type="link" collapse="Loesung_3_3_1_2_Lösungsweg">{{icon>eye}} Final result</button><collapse id="Loesung_3_3_1_2_Lösungsweg" collapsed="true"> |
| The values of the substitute resistor and the currents in the branches are |
| \begin{equation*} |
| \text{a)} \quad R=8~\Omega \qquad I=1.25~A \\ |
| \text{b)} \quad R=4~\Omega \qquad U=-5~V |
| \end{equation*} |
| </collapse> |
| </WRAP></WRAP></panel> |
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| {{page>task_3.1.3_with_calculation&nofooter}} |
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| ~~PAGEBREAK~~ ~~CLEARFIX~~ |
| ===== Common pitfalls ===== |
| * **Wrong deactivation:** do **not** set an ideal voltage source to open or an ideal current source to short; the rules are: $U$-source→**short**, $I$-source→**open**. |
| * **Confusing goals:** **max power** ($R_{\rm L}=R_{\rm i}$, $\eta=50\%$) vs. **high efficiency** ($R_{\rm L}\gg R_{\rm i}$). Don’t equate them. |
| * **Ignoring ratings:** not every real source is short-circuit-proof—$I_{\rm SC}$ is a **model parameter**, not a recommended experiment. |
| * **Mixed conventions:** keep the **passive sign convention** for loads; use conventional current ($+$ to $-$). |
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| ~~PAGEBREAK~~ ~~CLEARFIX~~ |
| ===== Embedded resources ===== |
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| <WRAP column half> |
| DC Voltage & Current Source Theory |
| {{youtube>AQK7RyecVW0}} |
| </WRAP> |
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<WRAP column half> | <WRAP column half> |
{{youtube>w4N9CBc_nkA}} | {{youtube>w4N9CBc_nkA}} |
</WRAP> | </WRAP> |
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<WRAP column half> | <WRAP column half> |
A more complex superposition example | A more complex superposition example |
* A **linear (real) source** is fully determined by $(U_{\rm OC},I_{\rm SC})$ or equivalently $(U_0,R_{\rm i})$ / $(I_0,G_{\rm i})$; both forms are **equivalent**. | * A **linear (real) source** is fully determined by $(U_{\rm OC},I_{\rm SC})$ or equivalently $(U_0,R_{\rm i})$ / $(I_0,G_{\rm i})$; both forms are **equivalent**. |
* **Thevenin ↔ Norton**: $U_{\rm OC}=I_{\rm SC}R_{\rm i}$, $G_{\rm i}=1/R_{\rm i}$; deactivation rules let you find $R_{\rm i}$ quickly. | * **Thevenin ↔ Norton**: $U_{\rm OC}=I_{\rm SC}R_{\rm i}$, $G_{\rm i}=1/R_{\rm i}$; deactivation rules let you find $R_{\rm i}$ quickly. |
* **Efficiency vs. maximum power**: choose $R_{\rm L}\gg R_{\rm i}$ for high $\eta$, or $R_{\rm L}=R_{\rm i}$ for max $P_{\rm L}$. | |
* **Two-terminal reductions** (e.g., loaded divider) simplify analysis of larger networks. | * **Two-terminal reductions** (e.g., loaded divider) simplify analysis of larger networks. |
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