Having a larger group than most of the other groups in the class, there were a lot of ideas swirling around during the decision process of picking an experiment to do in class. We all had one project that intrigued us. We came back the next class and look more into the process of each experiment and decided that looking into Acid Rain might be the most interesting. Giving what we talked about in class about sustainability and climate, we thought that acid rain was a relevant topic to the class that the class would enjoy very much.
Category: Experiments/Labs
Generator Lab
This lab was aimed at proving Faraday’s law. Faraday’s law states that a change in magnetic flux through coiled wires will generate an electrical current and voltage. It also states that the greater then change in magnetic flux, the greater the generated current and voltage will be. This was demonstrated through a combination of an NXT attachment as well as a generator apparatus taken from a flashlight.
By shaking the light the magnet passes through the coil and thus generates an electric charge. The NXT read the voltage generated over a 30 second period and saved it to an excel table. We then took the sum of the square values it recorded to determine the level of electrical charge. We can see that as the number of shakes increases, the current and voltage increase.
After some initial confusion the lab ended up successfully proving Faraday’s Law despite a two minor problems:
Data not recording properly
Narrow set of data (most of the data falling between 90 and 120 shakes)
Tom Vales Visits Class
Professor of electrical engineering Tom Vales came to class to show us different alternative energy machines that he had collected and built. Each one displayed a different method of creating electricity. His visit gave us great insight into how science and technology is striving to find the best ways to create energy without harmful effects on the environment.
The first machine he showed us was called a Stirling Motor/Engine. This machine was particularly interesting because it was operating solely on steam created by a pot of boiling water. The steam from the water creating a shifting airflow within a tube, which in turn drove a piston, which could then be used to generate a form of essentially free energy. He said that this technology was utilized in emergency generators in Maine.
Next, Mr. Vales showed us a machine that was invented by physicist Jean Peltier. The machine incorporated two types of electricity conducting metal, copper and bismuth, fused together. An electric charge is sent through one side of the machine, heating up the other end which can then be used for different purposes.
The next machine was referred to as a Mendocino Motor. This device was very impressive, as it used nothing but solar energy to operate and resulted in a long metal rod actually floating and spinning freely in a magnetic field. This was accomplished by attaching four solar panels to the rod and concentrating a light source over the cells. The cells generated a charge that each turned the rod 90 degrees, and since there are four cells the rod spun in a full circular motion for as long as the light source was turned on. This demonstration impressed me because it showed solar energy could create a type of perpetual motion machine in a small scale machine.
Lastly, Mr. Vales demonstrated a Tesla Coil that he built himself. The Tesla Coil works by creating an alternating current of electricity through tightly spun copper wire. This demonstration showed us how AC power flows through different devices, which is how electricity flows from electrical outlets in our walls to any type of device we plug into the outlet. The Tesla Coil was very impressive and interesting, and Mr. Vales demonstrating how the electricity flowed through various devices he brought helped me better understand the concept of alternating current.
Force and Energy
Our second experiment using the NXT system was to demonstrate the relationship between acceleration, mass, and force using a pulley system and weights. The goal of the experiment was to prove Newton’s second law of motion. Newton’s second law states:
Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).
Meaning: FORCE = MASS x ACCELERATION.
From Newton’s second Law we know that a heavier mass requires more force (energy) to be moved.
So, in this experiment we would test this law in two ways using a pulley and weight system. First, we tested the pulley system using one constant power level (60%) while changing the amount of mass on the pulley. Next, we kept mass constant while changing the power levels.
The expected and proven relationships are:
Decrease in upward Acceleration with stable power and increasing mass
- Demonstrated by the equation (F=m*a)
Increasing upward Acceleration with stable mass and increasing power
- Demonstrated again by the equation (F=m*a)
Here is an excel spreadsheet of our results:
Next, we used our measurements to create tables and graphs to visualize the results that we found.
Above you can see the results of keeping power constant at 60% while changing mass. Seeing that with constant force, the larger the mass became, slower the acceleration. The affect it has on acceleration is in concurrence with Newton’s Law because with more mass, the pulley needed more power to have a higher acceleration.
- Power = 60
Mass = 0.245 kg
Acceleration = 24.064736 - Power = 60
Mass = 0.19 kg
Acceleration = 29.212683 - Power = 60
Mass = 0.15 kg
Acceleration = 33.443774
Here you can see that we changed the power level while keeping mass constant at 0.15kg. Once again the results concur with Newton’s Law because we see that the higher the force on an object, the more acceleration that object is going to have.
- Power = 40
Mass = 0.15 kg
Acceleration = 11.328434 - Power = 80
Mass = 0.15 kg
Acceleration = 60.382472
Lego Mindstorm
For our first official experiment with the Lego Mindstorm NXT platform we used LabView to power the wheels and compare the distance it calculated to the distance we measured. For the most part LabViews calculations were close (10% error or under), with the average percent error being 8.07%.
You can read our measurements here, or in an excel spreadsheet attached below:
| Power Setting | Time(s) | Number of Turns | Left Wheel Rotation | Right Wheel Rotation | Velocity (m/s) | Distance Calculated (m) | Distance Measured(m) | Percent Error |
| 75.00 | 1.00 | 1.52 | 552.00 | 546.00 | 0.27 | 0.27 | 0.28 | 2.50 |
| 75.00 | 1.00 | 1.53 | 554.00 | 549.00 | 0.27 | 0.27 | 0.29 | 5.34 |
| 75.00 | 1.00 | 1.52 | 551.00 | 546.00 | 0.27 | 0.27 | 0.29 | 5.86 |
| 50.00 | 1.00 | 0.95 | 345.00 | 342.00 | 0.17 | 0.17 | 0.19 | 10.00 |
| 50.00 | 1.00 | 0.93 | 338.00 | 335.00 | 0.17 | 0.17 | 0.19 | 11.84 |
| 50.00 | 1.00 | 0.95 | 345.00 | 341.00 | 0.17 | 0.17 | 0.18 | 5.28 |
| 25.00 | 1.00 | 0.39 | 143.00 | 142.00 | 0.07 | 0.07 | 0.08 | 5.33 |
| 25.00 | 1.00 | 0.39 | 140.00 | 139.00 | 0.07 | 0.07 | 0.08 | 13.13 |
| 25.00 | 1.00 | 0.36 | 130.00 | 132.00 | 0.07 | 0.07 | 0.08 | 13.33 |
For easier reading: Lego NXT Post1
The difference between measured and the LabView’s calculated values are not spontaneous or without probable cause. The calculations done were based off of rounded values and used a circumference for the wheels that was estimated using a ruler, which has a fairly low accuracy.
Another problem that arose occurred before we started our measurements. It appeared that we couldn’t figure out how to properly assemble the the third wheel of the car. At first, the tire was rubbing against the body, thus causing it drag and slow movement. Upon adjustment, the wheel would not stay straight, thus turning the car even when both motors were evenly powered.
The last most likely source of error is the inconsistency in starting position during trials. While we attempted to keep the starting point consistent, it is unreasonable to expect a perfectly uniform system of measurement given the materials at hand.
NXT Side View
A fun experiment and neat introduction to LabView, though the assembly did become frustrating, but it will be interesting to see how else we use the NXT platform, and what other experiments lay ahead. I wish we had utilized a larger space rather than a desktop in class, but we made due with what we had.