Experiment 2: Capacitor Bottle Shapes

Using the results of the previous experiment, we set out to determine which bottle shape matched our goals the most.

Purpose:
The purpose of this experiment is to determine which of two types of bottle shape (tall and thin or short and fat) would meet our criteria of high capacitance and ease of preparation.

Hypothesis:
The group's hypothesis was that the taller, thinner bottle shape would meet our criteria the best because of the narrow radius of the bottle, the high surface area of the exterior, and the affordability of the drink that came with it (orange cream soda).

Variables:
Control
Concentration: All salt-water used in this experiment is 26.9 g / 300 mL of water.
Liquid: We chose to use 300 mL ± 1 mL of pure deionized water.
Salt: We chose to use "Diamond Crystal Kosher Salt" as our salt.
Foil: We chose to use "Reynolds Wrap Quality Aluminum Foil" as our foil.
Oil: We chose to use "Arco Supreme Motor Oil" as our oil.

Varied:
Bottle shape: We chose a tall and thin bottle and a short and fat bottle.
Oil: We chose to place oil nowhere in the system, only in the capacitor bottle, and in the bottle and tub at the same time.

Equipment:
Today's experiment used the following materials:

• 2 200 mL beakers to hold salt in (120 g each)
• 1 500 mL graduated cylinder
• 1 orange cream soda bottle, cleaned thoroughly
• 1 short and fat bottle, cleaned thoroughly
  
• Aluminum foil
• Kosher salt
• Deionized water
• Weights and mass measuring devices
• Funnel to aid pouring of salt
• Motor oil
• Large plastic bin
• Electric tape
• Multimeter

Procedure:

1. We wrapped the interior of the bin with two layers of tin foil, sealing the edges with electric tape and prepared the two bottles with foil and lids.
   
2. We filled both bottles with 300 mL of our salt-water.
3. We placed the bottles, and a few more bottles purely for displacement purposes, into the bin.
4. We filled the bin with 7000 mL of the salt-water, which used up our cache of salt.
5. We placed one probe on the foil lining the bin and one probe on each bottle's conductive core using the multimeter. We measured the resulting capacitance.
6. Repeat step 5 with motor oil only in the bottle and motor oil in the bottle and the surrounding fluid to detect any changes in capacitance.
   

Results:
Table 2.1: Capacitor bottle shapes and capacitance

Bottle	Oil	Ratio of Salt to Water	Capacitance (nF) ± 1 nF
Tall and Thin	None	26.9 g / 300 mL	2
	Bottle only	26.9 g / 300 mL	2
	Bottle and tub	26.9 g / 300 mL	2
Short and Fat	None	26.9 g / 300 mL	2
	Bottle only	26.9 g / 300 mL	2
	Bottle and tub	26.9 g / 300 mL	2

Analysis:
The results show that the salt water capacitors are not affected by the size to a measurable amount with our techniques. Since this makes the capacitance of our criteria equal, the only difference between the two bottle shapes is the ease of preparation. Since the group immensely enjoyed purchasing the economically affordable orange cream soda and then drinking it, as well as wrapping the bottles in foil, the group has decided that the tall and thin bottles (the orange cream bottles) are the chosen bottles for our capacitors.

Because the oil status did not affect the capacitance directly to a measurable amount with our techniques, we are going to rely on our understandings of the motor oil's purpose to make that decision. From what our research has suggested, ionized salt water (which would be created in the process of charging our capacitors) creates 03 in contact with the air, which is a volatile and toxic gas. To reduce the risk of spontaneous explosions from the capacitor, we are using the motor oil to act as a barrier between the atmosphere and the salt water.

Further questions include what type of motor oil to use, specifically detergent or non-detergent. We also want to understand the relationship between salt-water concentration and capacitance in more detail.

Attendees:
Nate
Dan
Eric
Jodi
Matt