

Parallel Circuits Lab
Objectives:
1. Observe the Characteristics of Parallel Circuits.
Procedure:
1. Calculate and measure RT for the following circuits:
Figure 1: Parallel Resistive Networks
2. Calculate and measure R_{T}, V_{1}, V_{2}, V_{3}, I_{1}, I_{2}, I_{3},
I_{t}, and I_{a} for the circuit in Figure 2.
3. Use the measured values from step 2 to:
a. Verify the characteristics of parallel circuits (R_{T}, V_{R1} = V_{R2}, etc)
b. Verify KCL
c. Verify the current divider principle
4. What resistance in (series) (parallel) with the network in Figure 2 will result in I_{t} = 10mA.
Verify your calculations experimentally by measuring I_{t}.
5. What resistance in (series) (parallel) with the network in Figure 2 will result in I_{t} = 4mA.
Verify your calculations experimentally by measuring I_{t}.
Procedure & Data:
Part 1:
To calculate R_{T} for the following circuits this equation must be used. Calculated and measured results are provided with a
comparison of each of the circuits and percent differences
R_{T} = 1 / [ (1/R_{1}) + (1/R_{2}) + (1/R_{3}) + ... ]
Figure 1a: Section 1 Results
Part 2:
For this section, calculated and measured values for R_{T}, V_{1}, V_{2}, V_{3}, I_{1}, I_{2},
I_{3}, I_{T}, and I_{a} for the circuit in Figure 2a. The voltage in a parallel circuit is the same acrossed each resistor,
so V_{R1} = V_{R2} = V_{R3} = 15V
Using Ohms Law, and solving for I we get I = V/R, so:
I_{1} = 3.19mA
I_{2} = 1.5mA
I_{3} = 1.5mA
I_{T} = 6.19mA
I_{a} = I_{2} + I_{3} = 3.0mA
Part 3:
By using the measured values from Step 2, the following characteristics for the parallel circuits can be verified using the circuit analysis
techniques, KCL and the current divider principle.
I_{1} = I_{T}  I_{a}, Therefore: I_{1} = 3.21mA
I_{3} = I_{1}  I_{2}, Therefore: I_{3} = 1.52mA
I_{2} = I_{3}, Where: I_{2} = 1.52mA
Part 4:
For I_{T} = 10mA, a resistance of 3.93kΩ must be added in parallel to the circuit in Figure 2.
In practical terms, a 4kΩ has been added to the circuit because it is the nearest available value.
Given the 5 percent tolerance error this should be acceptable.
Part 5:
For I_{T} = 4mA,a resistor of 1.33kΩ must be added in series to the circuit in Figure 2.
Conclusion:
The main idea I obtained from this lab was that if the amperes of a circuit increases, then the resistance of that circuit must decrease.
Also if the amperage of the circuit decreases then the resistance of the overall circuit must increase. They resistance and current are tied
to each other, if once changes the other must also change. It was also noted that to get an increase in amps, a resistance must be added to
the original circuit in parallel, and for a decrease in amps, a resistance must be added to the original circuit in series.
Electrical Engineering lab key words: Ohms Law, KCL, total resistance, measured vs. calculated, current divider, circuit balancing, resistor,
networks, current measurement, voltage measurement, parallel circuit, electronics lab experiment.
