184_projects:lightbulbs_r_us_24 [Projects & Practices in Physics]

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===== Project 6A: Lightbulbs'R'Us =====

==== Kick Off Questions ====
  - There are a lot of new vocab words this week. For each of these words, write out the variable, the definition (what is it in words), and the units: electron mobility, electron density, conductivity, resistivity, resistance, electron current, conventional current, voltage, power, and drift speed. (Write these in your Facts Quadrant.)
  - Thinking about an incandescent lightbulb - what is a filament? How does this type of lightbulb produce light? (Feel free to look it up!)
  - What equation would you use to calculate the resistance of a lightbulb if you know the material, length, and area of the resistor? What equation would you use to calculate the resistance if you know the voltage and current of the light bulb? What equation would you use to calculate the resistance if you know the power and current? (Write these equations in your facts quadrant - you'll need them later!)

==== Main Problem ====
{{  184_notes:wires.png?200}}

Your team is continuing to help repair FTOE's Hawkion accelerator.  The accelerator engineers want warning lights so that they know when the power delivery system is operating, and they have told you that a current of 2.5 A down the carrier wire should turn on the warning light.  But with Lakeview still sealed off by rogue thunderstorms they can't order LED bulbs and will need to construct lightbulbs the old-fashioned way using a filament (very thin piece of wire, diameter = 0.1 mm) connected to the carrier wire (normal electrical wire, diameter = 1.63 mm). You happen to have the following [[184_notes:metals|metals in the warehouse]], with known electron densities and electron mobilities. 

The engineers have asked for a product report on your design. They would like you to outline which metals you would want to use for carrier and filament, why you picked those metals, and the expected surface charge distribution for your set up. They would also like to know the total resistance of your design and the total voltage needed to power your bulb (so they know what kind of battery to provide). 

<WRAP info>
=== Learning Goals: ===
  * Describe what parts of the circuit provide power and which parts use power.
  * Compare quantities like current, electric field, potential difference, and power for the thin and thick parts of the wire.
  * Describe and draw the surface charge gradient for a thick and thin wire.
  * Explain what is resistivity/conductivity and how it relates to resistance.
  * Explain how current, voltage, and resistance are related and how you used these ideas in your solution.
</WRAP> 

==== Wrap Up Questions ====
  - How does the current compare in the filament and carrier wires? (Same, bigger, smaller?) How does the electric field, potential difference, and power compare for the different wires? (Same, bigger, smaller?)
  -  What is the drift speed of the electrons in the wire? How long would it take one electron to travel the whole circuit? (You can calculate a numbers here.) Why would the lights turn on immediately when you flip a switch?
  - A key assumption for this problem (and this unit) is that the resistor is an "Ohmic resistor" - what does this mean?
  - What other assumptions did you make in your solution? Why did you need them?
  - What materials are typically used for lightbulbs? Does this match your solution? What other factors might be a large influence in the choice of metal? 

/*
Group Project Prep:
  - Discuss with your group how you actually want to complete the project. (Google doc? Physical whiteboards? Jamboards? On paper?)
  - Review the Group Project rubric together as a group (in Group Project 1 folder on D2L). This is what we'll be using to grade your write ups.
  - Review the learning goals & conceptual questions on the in class problems from Weeks 1 - 4. Make sure you know how to address those!
  - Review the in class problems from Weeks 1 - 4. Were there any you feel shaky on? Did you not get to a certain part on any? (e.g. did you not really talk about assumptions on Project 2A?) Flesh out your solutions and add any missing parts/detail.
*/