Network Theorems - Lecture 2
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Questions and Answers

What is the first step in applying Millman’s theorem?

  • Combine series voltage sources.
  • Convert all voltage sources to current sources. (correct)
  • Convert all current sources to voltage sources.
  • Calculate the total resistance of the network.

Which scenario is not applicable for using the Substitution Theorem?

  • When the voltage across the branch remains constant.
  • When the voltage and current of a single branch are known.
  • When replacing a resistor with a different resistor.
  • In networks with two or more sources not in series or parallel. (correct)

What does the Reciprocity Theorem state about current due to a voltage source?

  • The current remains the same regardless of the source's position. (correct)
  • The current will be zero if the source is moved.
  • The current changes based on the resistance values in the circuit.
  • The current will double if the source is moved.

Which statement describes the equivalent resistance in Millman’s theorem?

<p>It represents the total resistance seen by the resulting current source. (B)</p> Signup and view all the answers

What must be true for branch equivalence in the Substitution Theorem?

<p>The terminal voltage and current must be the same. (C)</p> Signup and view all the answers

What is the superposition theorem primarily used for?

<p>Analyzing networks with two or more sources that aren't in series or parallel (D)</p> Signup and view all the answers

What should be done when removing a voltage source from a network schematic?

<p>Replace it with a direct connection (short circuit) of zero ohms (A)</p> Signup and view all the answers

How do you calculate the total current using superposition?

<p>By taking the algebraic sum of the individual currents from each source (A)</p> Signup and view all the answers

What remains in the network when a current source is removed?

<p>The internal resistance associated with the current source (C)</p> Signup and view all the answers

In Example 1, what is the value of the total current I1 after applying the superposition theorem?

<p>5A (C)</p> Signup and view all the answers

What does Thévenin's theorem allow you to do with a two-terminal DC network?

<p>Replace it with a voltage source and series resistor (B)</p> Signup and view all the answers

What is the first step in the Thévenin's theorem procedure?

<p>Remove the portion of the network (C)</p> Signup and view all the answers

What happens when both sources are active in a circuit according to the superposition theorem?

<p>The effects of each source can be combined to find the overall current (C)</p> Signup and view all the answers

What does the superposition theorem state about the voltage across any element in a network?

<p>It is equal to the algebraic sum of the voltages from each source independently (C)</p> Signup and view all the answers

How is the Thévenin resistance (RTh) calculated?

<p>By finding the resultant resistance with all sources set to zero (C)</p> Signup and view all the answers

What happens to a voltage source when calculating RTh?

<p>It is replaced by a short circuit (A)</p> Signup and view all the answers

In Example 2, what is the equivalent resistance for resistors R2 and R3 when using the superposition theorem?

<p>3Ω (D)</p> Signup and view all the answers

How do you calculate the Thévenin voltage (ETh)?

<p>By reconnecting the sources and measuring the open-circuit voltage (B)</p> Signup and view all the answers

In Example 5, what is the value of RTh calculated?

<p>6 W (B)</p> Signup and view all the answers

What is the final step in producing the Thévenin equivalent circuit?

<p>Drawing the equivalent circuit with the removed component reconnected (D)</p> Signup and view all the answers

If current sources are present while calculating RTh, how are they treated?

<p>They are replaced by short circuits (D)</p> Signup and view all the answers

What is the value of RTh for the given network?

<p>2 kW (C)</p> Signup and view all the answers

What must be included when setting voltage and/or current sources to zero in a circuit?

<p>Internal resistance of sources (B)</p> Signup and view all the answers

After applying the superposition theorem, what is the value of ETh?

<p>3 V (D)</p> Signup and view all the answers

What is the formula used to calculate Rb in the provided solution?

<p>Rb = (R1 * Ra) / (R1 + Ra) (B)</p> Signup and view all the answers

How is the Norton current (IN) calculated in the network?

<p>By finding the short-circuit current between the marked terminals (C)</p> Signup and view all the answers

When does maximum power transfer occur in a network?

<p>When the load resistance equals the Thévenin resistance (D)</p> Signup and view all the answers

Norton's Theorem states that a linear bilateral dc network can be replaced by which of the following?

<p>A current source and a parallel resistor (B)</p> Signup and view all the answers

What does Millman's Theorem allow for regarding multiple voltage sources?

<p>To combine them into a single voltage source (D)</p> Signup and view all the answers

How is RN calculated in Norton's Theorem?

<p>By short-circuiting all voltage sources and open-circuiting current sources (C)</p> Signup and view all the answers

What would happen if E1 was not replaced with a short circuit while calculating E'Th?

<p>The calculation would yield an incorrect total voltage (A)</p> Signup and view all the answers

How can the Norton and Thévenin equivalent circuits be derived from each other?

<p>Through source transformation (D)</p> Signup and view all the answers

Which component values are used to compute RTh?

<p>Rb and R4 (C)</p> Signup and view all the answers

What happens to the Norton current when the load is short-circuited?

<p>It remains unchanged as long as sources are consistent (B)</p> Signup and view all the answers

What role do E' and E'' play in finding ETh?

<p>They are used in the subtraction to identify polarity change (B)</p> Signup and view all the answers

In calculating maximum power delivered to a load, what power equation is primarily used?

<p>$P = IV$ (C)</p> Signup and view all the answers

What does the short-circuit current between terminals indicate in a Norton equivalent circuit?

<p>The current that would be measured by an ammeter placed between terminals (B)</p> Signup and view all the answers

What is the total current $I_2$ through resistor R2 when both sources are active?

<p>8 A (C)</p> Signup and view all the answers

What is the value of $R_T$ when using resistors R1 and R2 in series?

<p>12 W (B)</p> Signup and view all the answers

According to the superposition theorem, when a current source is replaced by an open circuit, what happens to the current flowing through R2?

<p>It becomes 0 A (A)</p> Signup and view all the answers

What is the calculated power, $P_2$, when both sources are considered?

<p>384 W (A)</p> Signup and view all the answers

Why is the superposition theorem not applicable to power levels?

<p>P_total does not equal the sum of individual powers (A)</p> Signup and view all the answers

What is the effect of using Thévenin’s theorem on electronic networks?

<p>It reduces the number of components needed (B)</p> Signup and view all the answers

What happens to the current $I'2$ through R2 when the voltage source is short-circuited?

<p>It becomes 6 A (B)</p> Signup and view all the answers

What is the resistance $R_T$ when R3 is in parallel with R1 and R2?

<p>12 W (C)</p> Signup and view all the answers

Flashcards

Superposition Theorem

A circuit analysis method where each source (voltage or current) is considered independently, and then their effects are combined to get the overall solution.

Removing Sources for Superposition

When analyzing a circuit for a specific source, all other voltage sources are replaced with short circuits (zero resistance) and all current sources are replaced with open circuits (infinite resistance).

Combined Effects in Superposition

The total current or voltage in a circuit is the algebraic sum of the contributions from each individual source.

Thévenin's Theorem

A theorem used to simplify complex circuits by replacing a network of sources and resistances with an equivalent single voltage source and a single series resistor.

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Norton's Theorem

A theorem used to simplify complex circuits by replacing a network of sources and resistances with an equivalent single current source and a single parallel resistor.

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Maximum Power Transfer Theorem

A theorem that helps find the maximum power that can be delivered from a source to a load.

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Millman's Theorem

A theorem that helps to calculate the voltage at a node in a circuit with multiple sources.

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Substitution Theorem

A theorem that allows for the replacement of a part of a circuit with an equivalent without changing the behaviour of other parts of the circuit.

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Total series resistance (RT)

The total resistance in a circuit with multiple resistors connected in series.

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Total series current (I's)

The current flowing through a circuit with multiple resistors connected in series. This is the same current that flows through each resistor.

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Current in series (I'2)

Calculating the current flowing through a specific resistor (R2) in a series circuit, based on the total series current (I's) and the resistances involved.

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Power dissipated by a resistor

The power dissipated by a resistor when a specific current (I'2) flows through it.

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Current Divider Rule

A method used to calculate the current flowing through a specific resistor when multiple resistors are connected in parallel.

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Total Parallel Resistance

Calculating the total resistance in a circuit with parallel resistors.

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Calculating RTh

To find the Thévenin resistance (RTh), set all voltage sources to short circuits and current sources to open circuits. Then, calculate the resistance between the two terminals.

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Calculating ETh

To find the Thévenin voltage (ETh), return all sources to their original positions and calculate the open-circuit voltage between the terminals.

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Thévenin Equivalent Circuit

The simplified circuit consists of the Thévenin voltage source (ETh) in series with the Thévenin resistance (RTh).

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Step 1: Remove External Component

Remove the component external to the network where you want to find the Thévenin equivalent.

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Step 2: Set Sources to Zero

Replace voltage sources with short circuits and current sources with open circuits.

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Step 3: Calculate RTh

Calculate the resistance (RTh) between the marked terminals.

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Step 4: Restore Sources

Reconnect all sources to their original values.

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Reciprocity Theorem

The current through any branch of a network due to a voltage source is equal to the current through the branch where the source was originally located if the source and current measurement positions are swapped.

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Millman's Theorem formula

For any number of parallel voltage sources, the equivalent voltage is the sum of the individual voltages divided by the sum of their conductances.

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Limitation of Substitution Theorem

This theorem cannot be used to solve networks with two or more sources that are not in series or parallel.

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Norton's Theorem - Internal Resistance

The internal resistance of voltage or current sources must be considered when calculating the Norton equivalent circuit.

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Norton's Theorem - Short-Circuit Current (IN)

The current measured between the terminals when they are shorted together.

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Norton Equivalent Circuit

The equivalent circuit for the original network, consisting of a current source (IN) in parallel with a resistor (RN).

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Norton's Theorem - Equivalent Resistance (RN)

The equivalent resistance of the original network, seen from the terminals.

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Maximum Power Transfer - Load Resistance

The load resistance that receives maximum power from the network.

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Maximum Power Transfer

Occurs when the load resistance is equal to the Thevenin resistance (RTh).

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Millman's Theorem - Voltage Source

The voltage source is the sum of the individual voltage sources divided by the sum of the reciprocals of their individual resistances.

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Thevenin Resistance (RTh)

The equivalent resistance of the Thevenin circuit, calculated by setting all voltage sources to zero and finding the resulting resistance between the two terminals.

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Thevenin Voltage (ETh)

The equivalent voltage source of the Thevenin circuit, calculated using superposition by replacing each source with its equivalent, finding the individual contributions, and summing them.

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Norton Current (IN)

The equivalent current source of the Norton circuit, calculated by finding the short-circuit current through the terminals of the original circuit.

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Norton Resistance (RN)

The equivalent resistance of the Norton circuit, equal to the Thevenin resistance, calculated by setting all sources to zero and finding the resulting resistance between the two terminals.

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Study Notes

Network Theorems - Lecture 2

  • Various network theorems exist to analyze circuits
  • Key theorems include Superposition, Thévenin, Norton, Maximum Power Transfer, Millman's, Substitution, and Reciprocity
  • Superposition theorem allows analyzing networks with more than one source that are not in series or parallel. The current/voltage across an element equals the algebraic sum of currents/voltages produced independently by each source.
  • To use the superposition theorem, independently analyze the effects of each source while setting others to zero (open circuit current source, short circuit voltage source).
  • Thévenin's theorem simplifies a network into a single voltage source and a series resistor. The procedure involves finding the Thévenin equivalent (open circuit) voltage and resistance.
  • Remove the portion of the circuit to be analyzed.
  • Mark the terminals in the portion of the circuit remaining.
  • Calculate the Thévenin resistance by setting all sources to zero (voltage sources shorted, current sources opened).
  • Calculate the Thévenin voltage by setting the load to zero.
  • Draw the equivalent circuit by replacing the portion of the network with the Thévenin equivalent circuit
  • Norton's theorem provides an alternative equivalent circuit to Thévenin's, using a current source and parallel resistor. The steps are analogous, with finding the Norton resistance and current to make the equivalent circuit.
  • Maximum Power Transfer theorem describes a condition to maximize power transfer from a network to a load, occurring when the load resistance equals the Thévenin resistance
  • Millman's theorem simplifies multiple parallel voltage sources to a single equivalent voltage source. The procedure involves finding the equivalent voltage and resistance.
  • Substitution theorem is used to replace parts of a network with an equivalent network of components preserving terminal characteristics; for branch equivalence, terminal voltage and current values remain the same
  • Reciprocity theorem states that the current in a branch of a network resulting from one voltage source in place equals the current through that original source's branch with the voltage source moved.

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Network Theorem - Lecture 2 PDF

Description

This quiz covers key network theorems used in circuit analysis, including Superposition, Thévenin, and Norton. It explains how to apply these theorems to simplify complex circuits and compute equivalent values. Perfect for students looking to enhance their understanding of electrical engineering concepts.

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