### EE 101 Lab Exercise 1: Ohm's Law, Kirchoff's Laws, and Conservation of Power

This exercise does not have to be completed in a comp book, but starting with the next lab, a comp book must be used.

Part I. Voltage and Current Measurements. SHOW ALL UNITS WHERE APPLICABLE!

1. Before building the circuit, using Ohm's Law, calculate the current through the 10K ohm  resistor. This is your theoretical value. Give your answer in amps (A), milliamps (mA), and microamps (uA).  Show your work to the right of Figure 1.  (1A = 1,000mA = 1,000,000uA)

Figure 1.
2. Voltage and current measurements.

1. Using a multimeter, measure the actual resistance of the 10K ohm resistor (before building the circuit).

2. Build the circuit in Figure 1 on the protoboard. With the multimeter set to measure DC volts, measure the voltage across the resistor.

3. One method used to measure the current through a resistor is to use Ohm's Law. Using the data you collected from 2a and 2b, calculate the current, I, through the resistor. Express your answer in milliamps. This is your experimental value.

4. Calculate the percent difference between the value for I you obtained in 2c, and the theoretical value for I you calculated in problem 1. Write your answer here.

5. Another method used to measure current through a resistor is to "break" your circuit, and insert the multimeter into it to complete the connection. Measure I using the multimeter. Write your answer here.

6. Calculate the percent difference between the value for I you obtained in 2e and the theoretical value for I you calculated in problem 1.

3. Using 10K ohm resistors, build the circuit in Figure 2 on your protoboard. Take care to lay out your circuit neatly, using wires of proper length where needed. Before connecting power to your circuit, adjust your power supply to 15 volts. Have a lab TA look over your circuit before you apply power to your circuit.

Figure 2.

1. Using a multimeter, the DC voltage across each circuit element.

2. Using Ohm's Law, calculate the values for all the indicated currents in the circuit.

3. Using Kirchoff's Current Law, write node equations for the currents entering and leaving Nodes 1, 2, and 3.

4. Using Kirchoff's Voltage Law, write loop equations for the three loops in the circuit.

5. Calculate the power delivered or absorbed by all circuit elements (Ps, P1, P2, P3, and P4). Show that the Law of Conservation of Power is observed by showing that power is balanced for the circuit.

Question:

1. What reasons can you think of that may explain why your experimental values for I were different than your theoretical values?

January 2001