184_projects:s21_project_7 [Projects & Practices in Physics]

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===== Project 7 =====

==== Project 7A: Level Up ====
Click on this pdf to access the activity: {{184_notes:week_8_-_coordination_level_up.pdf}}

This link has the answers to the Level Up Activity: {{184_notes:184_notes_level_up_answers.pdf}}

==== Project 7B: Dr. Walzule's Map Emergency ====
On one of Dr. Jackie Walzule's Jeep expeditions in the Upper Penisula, her phone charger cable suddenly stops working and she desperately needs her phone for directions/GPS. Isolated in the UP, she must pull a "MacGuyver" and create a charging circuit from the various circuit elements in her car's emergency kit. (Yes she carries circuit elements in her car for just such an occasion.) Dr. Jackie has started to draw out a circuit diagram that uses her car battery as a power source (12.5 V), but she is worried if she directly connects her phone to it, the battery will completely fry her phone. Instead, she has decided that it would be best to use the car battery to charge some capacitors and then discharge those through the phone. 

{{  184_notes:7bcircuit.png?500  }}

Dr. Jackie has asked your group (who were clearly hiking nearby) to help her fix the circuit, such that:
  - Her phone is never in direct contact with the battery.
  - The maximum current in the circuit (either charging or discharging) never reaches above 0.1 A.
  - The capacitor(s) would need to discharge 10-30 kJ to charge her phone. 

In her emergency kit, Dr. Jackie has two switches, a variety of 10 $\Omega$, 15 $\Omega$, 20 $\Omega$, and 25 $\Omega$ resistors, and a variety of 10 F, 100 F and 1000 F capacitors. She has told you to add any of the elements wherever you need in the circuit, as long as it meets those conditions. In your final solution, make sure you include: a circuit diagram with your added elements, a demonstration of how your circuit meets the criteria, and an explanation of what you expect in the circuit at different points in time (i.e. when is the switch opened/closed, where does current flow, is the capacitor charged/discharged at that point, charging/discharging graphs).

Remember, a good solution includes explanations, diagrams, evaluations, and commentary in addition to your calculations. See the Project Write Up Rubric for more details.

<WRAP info>
=== Learning Goals: ===
  * Design a circuit using a switch that charges and discharges capacitors
  * Use loop rule to determine voltage at different points in the circuit
  * Use resistors in series/parallel to control maximum current
  * Determine how to combine capacitors in series/parallel to reach desired energy
  * Explain what happens in the circuit in terms of current/voltage/charge over time
</WRAP>