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Question

A Norton equivalent circuit consists of a 100 μA current source in parallel with a 10 kΩ resistance. If this is converted into a Thevenin equivalent, how much is V Th ?

The correct answer is 1 V

Understanding the relationship between Norton and Thevenin equivalent circuits is fundamental in electrical circuit analysis. Both are simplified representations of a more complex linear circuit, but they use different approaches to model the behavior at a pair of terminals.

Norton Equivalent Circuit Basics

A Norton equivalent circuit simplifies any linear electrical network into an ideal current source ($I_N$) in parallel with an equivalent resistance ($R_N$).

  • $I_N$: This represents the short-circuit current that would flow if a short were placed across the terminals where the equivalent circuit is being determined.
  • $R_N$: This is the equivalent resistance looking back into the circuit from the terminals, with all independent voltage sources short-circuited and all independent current sources open-circuited. It is sometimes referred to as Norton resistance.

In this specific problem, we are given a Norton equivalent circuit with the following parameters:

  • Norton Current source ($I_N$) = 100 μA
  • Norton Resistance ($R_N$) = 10 kΩ

Thevenin Equivalent Circuit Basics

A Thevenin equivalent circuit, on the other hand, simplifies a linear electrical network into an ideal voltage source ($V_{Th}$) in series with an equivalent resistance ($R_{Th}$).

  • $V_{Th}$: This represents the open-circuit voltage that would appear across the terminals where the equivalent circuit is being determined. It is often referred to as Thevenin voltage.
  • $R_{Th}$: This is the equivalent resistance looking back into the circuit from the terminals, calculated in the same way as the Norton resistance ($R_N$).

Converting Norton to Thevenin Equivalent

The conversion between a Norton equivalent circuit and a Thevenin equivalent circuit is a common task in circuit analysis, as they are interchangeable representations of the same underlying circuit's terminal characteristics. The key relationships used for this conversion are derived from Ohm's Law and the principles of source transformation.

Conversion Formulas between Norton and Thevenin Equivalents
Parameter to Find Relationship to Known Norton Parameters
Thevenin Resistance ($R_{Th}$) $R_{Th} = R_N$
Thevenin Voltage ($V_{Th}$) $V_{Th} = I_N \times R_N$ (derived from Ohm's Law)

Since the question asks for the Thevenin voltage ($V_{Th}$), we will use the second relationship.

Calculating Thevenin Voltage ($V_{Th}$)

To determine the Thevenin voltage ($V_{Th}$) from the given Norton equivalent circuit, we apply the conversion formula $V_{Th} = I_N \times R_N$.

Let's list the given values and their standard units:

  • Norton Current ($I_N$) = 100 μA (microamperes) = $100 \times 10^{-6}$ A (amperes)
  • Norton Resistance ($R_N$) = 10 kΩ (kilo-ohms) = $10 \times 10^3$ Ω (ohms)

Now, substitute these values into the formula for $V_{Th}$:

$$ V_{Th} = I_N \times R_N $$ $$ V_{Th} = (100 \times 10^{-6} \text{ A}) \times (10 \times 10^3 \text{ Ω}) $$

To simplify the calculation, we can multiply the numerical parts and the powers of 10 separately:

$$ V_{Th} = (100 \times 10) \times (10^{-6} \times 10^3) \text{ V} $$ $$ V_{Th} = 1000 \times 10^{(-6+3)} \text{ V} $$ $$ V_{Th} = 1000 \times 10^{-3} \text{ V} $$

Since $10^{-3}$ means dividing by 1000:

$$ V_{Th} = 1 \text{ V} $$

Therefore, the Thevenin voltage ($V_{Th}$) for the equivalent circuit is 1 V.

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Important Questions from Thevenin's Theorem

  1. ______ is an analytical method used to change a complex circuit into a simple equivalent circuit consisting of a single resistance in series with a source voltage.

  2. According to the Thevenin's Theorem, any two terminal bilateral linear DC circuits can be replaced by an equivalent circuit consisting of:

  3. If Thevenin's voltage is 89.3 volts and Thevenin's resistance is 46.98 ohms then what will be the maximum power delivered to the load present in the network?

  4. Which of the following theorem states that "a linear two-terminal circuit can be replaced by an equivalent circuit consisting of a voltage source VTH in series with a resistor RTH", where VTH is the open circuit voltage at the terminals and RTH is the input or equivalent resistance at the terminals, when the independent sources are turned off

  5. For finding Thevenin equivalent circuit, the Circuit Current Sources have been replaced by:

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