In this project, we will emphasize interpreting circuit schematics and creating the corresponding physical circuits. Our circuit schematics will be for what are called lumped-parameters circuits; this simply means that our circuits are all created from idealized components which are connected by perfect conductors. In order to implement our circuits, we will also need to be able to identify nodes in the circuit—nodes simply correspond to single points in the circuit, electrically speaking. Confusion sometimes arises since the concept of an electrical point in a circuit is not necessarily the same thing as a single physical point; electrical nodes can be “spread out” by perfect conductors.
For this project, we will be using some components that we have seen from previous sections: voltage sources and resistors. However, we will give less guidance on exactly how to implement these components. For example, you will be expected to choose how to implement the required voltage source and you will need to find resistors in your parts kit corresponding to desired resistance values. Some additional information relative to the representation of sources in circuit schematics and reading color codes on resistors is provided at the links to the right.
One issue associated with implementing electrical circuits is whether the physical circuit actually corresponds to the one in the schematic—it is always possible that there is an error in the implementation, which results in testing a completely different circuit than what was intended. In order to ensure that we've actually created the desired circuit, we will need to measure some voltages and/or currents1. Expected values for these voltages and currents are provided in this project; if your measured values agree with the given values, you can be reasonably certain that your circuit is correct.
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Use V+ to apply 5V across the circuit.
The resistors limit the current.
In order to measure the current I, we need to re-configure the circuit to put the ammeter in line with the 10kΩ resistor.
The schematic to the right shows placement of the ammeter.
Label nodes (A, B, C, D) as points that connect two or more circuit components.
Each node on the schematic corresponds to a separate row of holes on your breadboard.
Arbitrarily pick different rows of holes in the breadboard and assign them to the nodes identified in part C.
Open WaveForms™ to view the main window.
Click on the Voltage instrument icon to open the Power Supplies window.
Turn on power to the circuit.
Your measured voltage should be approximately 2.5V.
Try reversing the polarity on your voltage measurement (just interchange the terminals). This should just change the sign on the displayed number.
Exchange the µA mA and COM terminals on the DMM. This should just change the sign of the current displayed on the DMM.
Use your DMM to measure the current through either of the 20kΩ resistors. You will need to reconfigure your circuit slightly in order to insert the DMM properly. Your measured current should be about 1.25mA.