Experiment 7 Norton’s Theorem

Aim:

Verification of Norton’s Theorem

Components and Equipment Required:
Variable power supply , 3 resistors, resistance box, constant current source, connecting wires

Theory:

 Norton’s theorem states that a linear two-terminal circuit can be replaced by an equivalent circuit consisting of a current source I_N in parallel with a resistor R_N, where I_N is the short-circuit current through the terminals and R_N is the input or equivalent resistance at the terminals when the independent sources are turned off.
The Norton’s equivalent current I_N is the short circuit current between the terminals when all voltage sources in network are short-circuited and all current sources are open circuited.

Circuit Diagram:

Procedure:

1. Perform steps, make the circuit on breadboard with a resistance box as R_L and a multimeter to measure voltage V_L across R_L. Set output of power supply.
2. Take out resistance from the resistance box and note down V_L as measured by Multimeter.
3. Vary R_L and note down the corresponding value of V_L.
4. Note down the load current I_L=V_L/R_L for each value of R_L.
5. Remove R_L, connect ammeter between terminal A and B and measures short circuit current I_SC. This is the Norton equivalent current I_N.
6. Remove R_L from the circuit and replace the power supply by a short circuit, measure the resistance between A and B directly with the multimeter.
7. Make the Nortons equivalent circuit, adjust the current from the current source. Take out the resistance and measure the lower resistance I_N the multimeter connected in series with a R_L
8. Vary R_L  and note down its corresponding values of I₁.
9. Compare the values of load current in the original circuit and in the Norton’s equivalent circuit for each value of R_L.
10. When current source is not available, connect a power supply in series with a variable resistance and milliammeter in place of the current source.

Observation Table:

                                                            Original circuit                                                Norton’s equivalent

R (Ω)	VL (V)	IL (mA)	VN	IN

Result:

The measured values of the load current and load voltage in the original circuit match the corresponding values in the Norton’s equivalent circuit.

Precautions:

1. The current in the circuit should remain constant for all observations
2. Set the voltmeter point at 0.
3. Check connections properly