Last week’s class, we discussed power in many forms. We had a lecture about nuclear power, and then delved further into the topic of power itself. We like to think of power and energy as being “generated,” which may be an incorrect term for it. All energy is already in existence, it is our job to transmute certain kinds of energy into other, usable forms of energy. In this lab, we experimented with this concept by using two forms of energy: electromagnetic and kinetic energy.
Using the NXT Lab Program, we attached our computer once again via USB cable to a device designed to measure our quantitative results, in this case, an electromagnetic flashlight. Using our own kinetic energy, we passed a magnet through an electromagnetic circuit that would in turn generate more energy from the interaction between the magnets. In this way, we could power the flashlight. By doing this, we saw how Faraday’s Law worked in real life, with quantitative results.
Discovered by Michael Faraday and Joseph Henry in 1831, Faraday’s Law describes the relation between the magnet’s speed in a closed circuit and the amount of energy produced. (Unfortunately for Mr. Henry, he didn’t publish his results before Faraday, otherwise we may be studying Henry’s Law!) The law is this:
The induced electromotive force (EMF) in any closed circuit is equal to the time rate of change of the magnetic flux through the circuit.
To see this illustrated, we used a set time interval and shook the magnet through the circuit a different number of times per interval to see what results we would get. Our set time interval was 30 seconds. For the first trial, we shook the magnet no times, then 10, then 20, then 30, and finally 40 times. The results of the lab were displayed on an Excel spreadsheet we created. Interestingly to us, our first trial, where we shook the magnet no times, still generated some energy, though we had expected none. The voltage was much lower than any of our other results, so perhaps this was the result of some stray energy stored within the flashlight. When we got our data, it was per second, so we squared the sum of the total voltage to determine how much actual energy we had generated. The results of the sums squared is as follows:
| # of Shakes | Sum Squared |
| 0 | 0.95 |
| 10 | 32.6 |
| 20 | 81.7 |
| 30 | 44.5 |
| 40 | 143.9 |
Lastly, based on this information, we made a graph of the results and included a line of best fit to show the general trend in energy generated.
Interestingly, for our fourth trail, where we shook the magnet 30 times, the data did not follow the trend of increasing voltage with increasing shakes. This may be human error, or maybe a technical malfunction of the part of the NXT software, but we felt it was important to note this irregularity, as it did not comply with Faraday’s Law!