University of California at Santa Cruz

Jack Baskin School of Engineering

EE-70L: Introduction to Circuits Laboratory

Laboratory 2

Ali Shakouri, 10/01/2000

 

Objective:
1. Voltage divider
2. Thevenin's equivalent circuit
3. Effect of load resistance
4. Superposition theorem

Prelab Questions

1. Use a constant voltage source at 10V and couple of resistors (from the following set: 10K, 22K, 39K, 47K, 68K, 82K, 100K, 150K, 220KW) to design a circuit that provides 2V (to within 10%) at its output. Call this circuit "alpha".

2. Derive the Thevenin equivalent circuit for alpha.

 

Lab

3. Build the circuit alpha and measure its output voltage (Voc).

4. Measure Isc .

5. From Voc and Isc deduce the Thevenin equivalent circuit for alpha ( Vth and Rth ). How this compares with the result in question 2.

6. In circuit alpha, remove the 10V constact voltage source and replace it with a short circuit. What is the measured resistance "seen" from the output? How this is related to Rth .

7. Connect a 1MW resistor to the output of circuit alpha and measure the voltage across this resistor (V1).

8. Replace the 1MW resistor with a 10W resistor and measure the voltage across it (V2).

9. Build the following circuit and measure the current flowing through 22KW resistor (I0).

10. In the above circuit replace the 15V power supply with a short circuit and measure the current flowing through 22KW resistor (I1).

11. In the above circuit put back the 15V power supply and replace the 10V power supply with a short circuit and measure the current flowing through 22KW resistor (I2).

12. Verify that (I0=I1+I2). This is called the superposition theorem.

 

Postlab Questions

13. Calculate the voltages measured in questions 7 and 8 using the Thevenin equivalent circuit for alpha.

14. How one could change circuit alpha to make the voltage at the output less sensitive to the value of resistance connected to it (load resistance)? Is there any drawbacks?

15. Calculate I0 in question 9, using the Thevenin equivalent circuit for alpha. How does it compare with the experimental value?