Challenge: To build, measure, diagram, and analyze a circuit made from salvaged components.
Parameters: The energy input will be a maximum 9.0VDC power adapter repurposed for this project. The current output and voltage of the adapter must be able to be measured at any time. The maximum current listed on the adaptor must be significantly more than your model uses when all components are on. The circuit should have a maximum footprint of 25 cm by 34 cm, but can be any height up to 82 cm. ie. IT MUST FIT IN YOUR LOCKER. The minimum number of components and complexity of the circuit can be increased each term, so make everything easy to change. Every component must be accessible for a voltage determination while operating. Each branch circuit must be able to operate alone (to allow for current measurement). Your project must include a correct circuit diagram with all components correctly represented, and a chart with the operating voltage, current, resistance, and power consumption listed for every component.
Scoring: Your project will be scored based on the accuracy of your diagram and analysis, and a class evaluation.
Physics: Ohm’s Law applies to any component in a circuit, but the resistance of a component may not be a constant. For example, motors, bulbs, and LEDs are non-Ohmic and their resistance at a particular applied voltage will not be constant for any other applied voltage. (It is very easy to destroy LEDs by using too much voltage, so we will have a lesson devoted to LEDs). Energy and mass conservation allow us to use junction and loop rules to find voltage and current anywhere in a circuit. Power can be easily calculated from current and voltage. Resistance of groups of components in series, parallel, or both can be mathematically determined and checked through measurement.
Extensions: The possibilities are endless, and you are encouraged to follow your interests, but you would not be expected to do a test question on things like transistors, which are not covered in class.
Help/Hints: Measure the operation of each component beforehand. You should know the best voltage to use, and the expected current, resistance, and power consumption for each component before building it in to your model. Try to make your wiring tidy, but easily accessible for fixing problems and doing measurements. Some components cannot be put in series because their current requirements are totally different. (For example, motors and LEDs)
Online Text: ch 19