course_planning:184_projects:s19_project_14 [Projects & Practices in Physics]

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===== Project 14 =====

==== Project 14A: Transformers: Magnetic Flux in Disguise ====
Back in Lakeview, the discovery of Dr. Watersa's illicit stash of jellybeans has shocked the town's residents. Not only has she been hiding delicious treats from her friends and neighbors, the town is also out-of-luck for the potential alternative energy source. In their anticipation of using the water mill for energy, the residents stupidly tore down all the ugly power lines. Now you have to help set them back up. You have access to a high-voltage power line from the edge of town, which has a voltage difference of $\Delta V = 240 \text{ kV } \cdot \sin(\omega t)$ compared to the ground, where $\omega = 60 \text{ Hz}$. You have access to the necessary safety equipment so you won't get electrocuted. You also have a plentiful supply of iron piping, which the town blacksmith has agreed to help you bend and mold as needed. Lastly, you have as much 12-gauge copper wire as you can imagine. Your goal is to devise a way to feed power lines to each house in Lakeview which don't exceed the maximum of 120 V compared to ground.

{{ 184_notes:project14_powerline_visual.png?600 |Power Line}}

<WRAP info>
=== Learning Goals ===
  * Explain how a voltage transformer works
  * Use the right hand rule to check the direction of the induced current.
  * Explain what it means for a power line to have a "voltage".
</WRAP>

==== Project 14B: Sending signals ====

You are able to use your successfully MacGyver'd metal detector to track what the EM-boar tigers have left behind and find your trapped team members. But it is not only your team members you find. It is the EM-boar tigers base of operations. More important than rescuing your team members you observed something in their lair that effects the whole of humanity and needs to be communicated immediately. You estimate there is about 1 hour and 50 minutes to figure out a way to send some sort of E&M signal out for rescue before the EM-boar tigers realize that you are planning an escape. (What will that signal be??? You decide.) Due to the sensitivity that EM-boar tigers have to E&M waves, you only have one chance to send the signal before they realize what is happening and close in on the team. You will need to make sure that the attempt will work. You have a small metal ball that can be charged up 1e-6 C without discharging in air. You've found a piston that can shake the ball a total distance of 2cm, but at nearly any frequency you need. Your team decides to create a model of the signal to determine how best to orient the setup, how much charge to dump on the ball, and how quickly to shake it. Your group has already started setting up the code.

<code>
GlowScript 2.6 VPython

## Objects

charge = sphere(pos = vector(0,0,0), radius = 0.001)
charge.v = vector(0,0,0)

## Constants and model parameters

q = 1e-6
k = 9e9
mu = 4*pi*1e-7
mofpi = mu/(4*pi)

## Set up time parameters

t = 0
dt = 0.1


## Create list of arrows that encricle the charge
## Each location has two arrows: one for E and one for B

N = 20
theta = 0
dtheta = 2*pi/N
R = 0.02
ArrowList = []

while theta < 2*pi:
    
    Loc = vector(R*cos(theta), R*sin(theta), 0)
    
    ArrowList.append([arrow(pos=Loc, axis = vector(0,0,0), color=color.cyan),arrow(pos=Loc, axis = vector(0,0,0), color=color.magenta)])
    
    theta += dtheta

## Calculation loop

while t < 1000:
    
    rate(100)
    
    ## Charge should oscillate
    
    
    ## Loop through arrows to make E and B vectors
    
    for Arrow in ArrowList:
        
        r = Arrow[0].pos - charge.pos

        E = vector(0,0,0)
        B = vector(0,0,0)

        Arrow[0].axis = E
        Arrow[1].axis = B
       
    t = t + dt
</code>

<WRAP info>
=== Learning Goals ===
  * Make predictions for the electric and magnetic fields from a moving charge over time
  * Model (using VPython/Glowscript) the electric and magnetic fields from an oscillating charge
  * Explain the effect of changing a variable on your model of the electric and magnetic fields (i.e., what would you expect to change if you changed the magnitude or sign of the charge)
</WRAP>