Thevenin's Theorem La Report,
EXPERIMENT NO. 10
Thevenin’s Theorem
Objectives:
1. To verify the Thevenin’s theorem through an experiment. 2. To find the Thevenin’s resistance RTH by various methods and compare values.
Equipment:
Resistors, DMM, breadboard, DC power supply, and connecting wires.
Theory:
Thevenin theorem states that any linear twoterminal circuit can be replaced by an equivalent circuit consisting of a voltage source VTH in series with a resistance RTH where
* VTH is the opencircuit voltage at the terminals, and
* RTH is the equivalent resistance seen thru the terminals provided that all the independent sources are turned off.
Finding VTH:
Determining the output voltage Vab in opencircuit condition (no load resistor meaning infinite resistance). This is known as the Thevenin voltage VTH. * i.e. VTH = Vab = VOC (opencircuit voltage)
Finding RTH:
There are different methods to find value of RTH as described below.
1. Method A:
(By measuring ISC – shortcircuit current)

Short the points ‘a’ and ‘b’, then measure the shortcircuit current Isc using an ammeter. Calculator RTH as follows
RTH = VTH/ ISC
Method 2:
(By measuring the equivalent resistance)
Remove all sources from the circuit, i.e. replace all voltage sources with a shortcircuit and current sources with an opencircuit. Then with the help of a multimeter find the resistance between the points ‘a’ and ‘b’, denoted by Req.
RTH = Req
Method 3:
(By applying known voltage and measuring source current).
We can also find RTH by applying a known voltage to the circuit between points ‘a’ and ‘b’, then measuring the current from the voltage source. Suppose 1 Vdc is applied as the test voltage then,
RTH = Vtest / I
4. Method 4:
(By inserting two different resistors and measuring current) There is another method to find the value of RTH, by inserting two different loads between points ‘a’ and ‘b’ i.e....
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