1. 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.)
2. Thinking about an incandescent lightbulb - what is a filament? How does this type of lightbulb produce light? (Feel free to look it up!)
3. 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!)

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 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).

1. 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?)
2. 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?
3. A key assumption for this problem (and this unit) is that the resistor is an “Ohmic resistor” - what does this mean?
4. What other assumptions did you make in your solution? Why did you need them?
5. 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?