Question

How do you calculate Thevenin and Norton equivalent circuits?

Answer 1

Calculating Thevenin and Norton equivalent circuits involves simplifying a complex network of resistors, voltage sources, and current sources into a simpler circuit that can accurately represent the original network's behavior from the perspective of a specific load.

Thevenin Equivalent Circuit:
The Thevenin equivalent circuit represents a network as a voltage source in series with a single resistor. To find the Thevenin equivalent, follow these steps:

Step 1: Identify the load resistance (R_L) for which you want to find the equivalent circuit.

Step 2: Remove the load resistor (R_L) from the original network. This might involve disconnecting or deactivating it.

Step 3: Calculate the Thevenin voltage (V_th) by determining the voltage across the load terminals with the load resistor removed. This can be done using various methods, such as voltage division or using Kirchhoff's laws.

Step 4: Calculate the Thevenin resistance (R_th) by looking into the network from the load terminals with all the voltage sources replaced by short circuits and all the current sources replaced by open circuits. Then, find the equivalent resistance between the load terminals.

Step 5: Draw the Thevenin equivalent circuit, which consists of a voltage source (V_th) in series with a resistor (R_th).

Norton Equivalent Circuit:
The Norton equivalent circuit represents a network as a current source in parallel with a single resistor. To find the Norton equivalent, follow these steps:

Step 1: Identify the load resistance (R_L) for which you want to find the equivalent circuit.

Step 2: Remove the load resistor (R_L) from the original network.

Step 3: Calculate the Norton current (I_N) by finding the current flowing through the load terminals when the load resistor is removed. This can be done using various methods, such as current division or using Kirchhoff's laws.

Step 4: Calculate the Norton resistance (R_N) by looking into the network from the load terminals with all the voltage sources replaced by short circuits and all the current sources replaced by open circuits. Then, find the equivalent resistance between the load terminals.

Step 5: Draw the Norton equivalent circuit, which consists of a current source (I_N) in parallel with a resistor (R_N).

It's important to note that while Thevenin and Norton equivalents provide a simpler representation of the original network, they are only accurate as seen from the load terminals. They do not represent the entire behavior of the original network with respect to different load conditions.