Lab #4 Thevenin’s Theorem CSSERVER实室# 4戴维南定理 csserver.docVIP

Lab #4 Thevenin’s Theorem In this experiment you will become familiar with one of the most important theorems in circuit analysis, Thevenin’s Theorem. Thevenin’s Theorem can be used for two purposes: To calculate the current through (or voltage across) a component in any circuit, or To develop a constant voltage equivalent circuit which may be used to simplify the analysis of a complex circuit. Any linear one-port network can be “replaced with” a single voltage source in series with a single resistor (see Figure 1 below). The voltage source is called the Thevenin equivalent voltage, and the resistor is called the Thevenin equivalent resistance. What this means is that a single voltage source and series resistor will behave identically to the actual part of the circuit it is replacing. In this experiment, you will use Thevenin’s theorem to solve a complex DC circuit. Figure 1 A network replaced with its Thevenin equivalent circuit The steps used for Thevenin’s Theorem are listed below: Step 1 Remove the resistor (R) through which you wish to calculate the current or across which you want to know the voltage. Label these terminals (where the resistor was removed) “a” and “b”. Calculate the voltage across these open terminals. This is called the open circuit voltage or the Thevenin equivalent voltage, VTH. Step 2 From the open terminals, (“a” and “b”) calculate the resistance “looking back” from the open terminals with all voltage sources removed and replaced by their internal resistances (if RInternal = 0, replace the voltage source with a short). This resistance is RTH. Now we have the components we need to create the Thevenin equivalent circuit as shown below using the Thevenin equivalent voltage and resistance values calculated above connected in series with the load resistor as shown below. Step 3 The current (through R) you wish to calculate will be: