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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 RT, V1, V2, V3, I1, I2, I3, It, and Ia for the circuit in Figure 2.



Figure 2: Parallel Resistive Circuit



3. Use the measured values from step 2 to:

a. Verify the characteristics of parallel circuits (RT, VR1 = VR2, 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 It = 10mA. Verify your calculations experimentally by measuring It.

5. What resistance in (series) (parallel) with the network in Figure 2 will result in It = 4mA. Verify your calculations experimentally by measuring It.


Procedure & Data:

Part 1:

To calculate RT 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

RT = 1 / [ (1/R1) + (1/R2) + (1/R3) + ... ]


Figure 1a: Section 1 Results


Part 2:

For this section, calculated and measured values for RT, V1, V2, V3, I1, I2, I3, IT, and Ia for the circuit in Figure 2a. The voltage in a parallel circuit is the same acrossed each resistor, so VR1 = VR2 = VR3 = 15V



Using Ohms Law, and solving for I we get I = V/R, so:

I1 = 3.19mA
I2 = 1.5mA
I3 = 1.5mA
IT = 6.19mA
Ia = I2 + I3 = 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.

I1 = IT - Ia, Therefore: I1 = 3.21mA

I3 = I1 - I2, Therefore: I3 = 1.52mA

I2 = I3, Where: I2 = 1.52mA


Part 4:

For IT = 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 IT = 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.

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