Monday, July 11, 2011

Who Says Resistors Can't Be Fun?

Last weekend, a new batch of students came to Penn on a summer program outside of Summer Discovery. They seem very nice (we played a game of ultimate Frisbee with a couple of them) but they made the dining hall exceptionally crowded this morning. It didn't help that I was running a little late. I opted for the reject bagel so I wouldn't have to wait for a new batch. I'm not exactly sure what flavor it was, but it wasn't bad.

My day just got better from there. In physics we have finished up lenses and light and are moving on to electricity and magnetism, a subject that has always interested me because it is the most difficult for me to understand. Bill had a unique analogy to offer, equating charged fields to gravitational potential energy shown on topographical maps. I appreciate Bill's unique and imaginative ways of describing things. They help me understand the material on a much deeper level.

During the morning lab, we worked with Scotch tape and paper bits and observed the basics of attraction and repulsion, which was quite fun, followed by a longer lab with our new lab group about the relationship between voltage and current. Last week, I had an all girls lab group, and this week I am the only girl so the experience is very different, but just as pleasant. And because in my new group, we have all taken physics before, the lab went much faster and we got a 10 minute break to all get to know each other. They are all very friendly, and I ended up seated with some of them at lunch.

For the afternoon lab, we had a blast. The task was to identify the relationship between resistance, length, and diameter of our resistor. In order to manipulate its shape, we uses the ever-so-high-tech Play Doh as our resister. Once the lab was finished, we were free to go, but instead we spent a couple minutes regressing into our childhood. As you can see:

After class today, I was exceptionally tired, so I took a nap before dinner. Once we ate, Alex, Brian and I showed a group of our friends the pond we saw on the first day and we spent some time there relaxing and digesting before a game of ultimate Frisbee.

Once it got dark, we hit the lounge and learned a British card game that was very exiting. Mostly because I won 4 rounds in a row (much to the dismay of the Brit who taught us). I am really grateful that this program gives us so much freedom and time to take a break from studying to just hang out, we are already becoming really close!

Charging Forward

Today, Alex and I switched up our morning routine a little bit. In the interest of getting a little extra sleep, yesterday evening we purchased some cereal and milk from the nearby convenience store. Instead of having to walk over to the dining hall and wait in line, we woke up an hour later and ate in our room. I’ve been having an absolutely amazing time here, but I’ve been a little short on sleep, so sleeping in felt great. 

With my newfound energy, we quickly walked over to class and took our seats. Bill began the day by discussing the idea of charge. Soon, we all pretended that we knew nothing about charge before we entered the room, and we followed Craig’s instructions to discovering how we know what we know about charge. While it might sound strange, we began to build our idea of charge using pieces of scotch tape. By putting a piece of tape adhesive side down on the table and then rapidly pulling it off, friction pulls off some electrons which charges the tape. We originally defined charged objects as objects that attract bits of paper when they are put in close proximity. We soon began to experiment with taping two pieces of tape together and then pulling them apart quickly which expanded our ideas of charge, because each of those pieces repelled each other. After some further experimentation with tape and other materials, we had a pretty good definition of what charge is, and it was time to move further with the ideas of electricity.

We all have a pretty good idea of what gravitational potential energy does. As humans, when we try to get further from the center of the earth, we must exert a large amount of energy to climb. This energy is stored as potential energy, and in the case that you fall or trip, it is converted back into kinetic energy from your motion. While we tend to think about it less than gravity in our daily lives, electric potential energy is similar to gravity in many ways. The first way to think about this is with two oppositely charged particles. Because opposites attract, keeping these particles separated takes a certain amount of energy which we call electric potential energy. With the ideas of electric potential energy solidified, we began to define some of the ways of describing this energy and what units are appropriate. We thought about ‘Volts’ as how much force per each charge is present. ‘Amps’ are a measure of how many charges flow through the circuit each second. Bill used the analogy of a stream to describe these concepts which many students find confusing. While voltage is analogous to how much water pressure is pushing water through a pipe, amperage is analogous to how much water is being forced through the pipe.

We then set out to discover a central theory of electricity that many people may remember from their high school physics class. We began our lab to attempt to verify Ohm’s law. We began by hooking up our circuit with a variable resistor and then adding a voltmeter and ammeter. Using Logger Pro, we could easily take and plot measurements of the voltage and current. After each point, we turned up the voltage, waited for the instruments to stabilize their readings and then recorded another point. By taking the slope of this line, we got a very clear relationship between voltage, current, and resistance. Our readings in the lab clearly verified the famous Ohm’s law which states that V=iR (Voltage is equal to current times resistance.) This kind of re-discovery of formulas that are otherwise quickly thrown at us in school has been very fun and interesting.

After class, I walked over to the gym to get rid of my extra energy. I got on the treadmill and ran for 2 miles at a quick pace and then tried out the Stairmaster to work some different muscles. After my cardio, I did a bit of stretching and yoga moves that I’ve learned over the past few years. The rest of the evening has been fairly relaxing. From hanging out in my room with Alex and friends, to playing a crazy game of ultimate Frisbee, and eating a delicious ice cream cone, I’ve had a lot of fun. I am enjoying being able to manage my own schedule a lot, and I’ve set a few goals for the remaining weeks:

1. Go to the gym at least 4 times each week.
2. Always ask questions when I am confused about the material in class.
3. Try to help my group members as much as they need with the labs and class work.
4. Make several new friends each day.
5. Get at least 7 hours of sleep each day.
6. Have a great time with my friends.

Maybe it’s a little cheesy, but hey it’s always good to set goals.

Not Your Average Monday

Today was different in a lot of ways. First of all, Brian and I slept in until 8:00 even though it was a class day. We decided to sleep in and just eat the cereal we bought for our dorm yesterday. We were actually able to get everything done before we needed to leave the dorm. We may have to do this more often, but then we would miss out on breakfast with our gang. Either decision is a great way to start the day.
Bill wearing his awesome shirt
Today, Bill walked into class wearing something completely unexpected. He always dresses casually, but today he was wearing a shirt displaying pictures of Chuck Norris’ emotions (you can see them below).

Today we moved on from our discussions on mechanics and moved on to electricity. The lecture began with an introduction to charges. As most people know, there are two charges, positive and negative. We also learned that should the day come when more charges are discovered, their symbols will be the symbols for multiplication and division. At first, I thought this was a joke, but apparently it was a serious statement. In the middle of the lecture, we had a mini-lab testing the charges in tape. We ripped off pieces of tape from our desks and observed what materials they were repelled or attracted to. The lecture continued with discussions of voltage and current. Bill put it in a way that made the differences that much clearer. He described voltage as the quality of electricity and current as the quantity of electricity. I had already known this, but this perspective made the concepts that much easier to understand.

Bill wearing his awesome shirt.
Ryan (one of our TAs) covers the post-lab
After our lecture, we went into the lab to test the relationship between voltage and current. Before we could do that though, we had to get into our new lab groups. I was grouped with Onur, Lindsay Holcomb, and Michael Iskhakov. Lindsay is from New York and Michael is local to Philadelphia and has to commute to campus every day. They are both nice people and I look forward to getting to know them this week. In the lab, we used what seemed to be a military surplus battery from World War II. This battery was massive and was about a foot in length and about six inches wide and tall. We connected the battery to a resistor that was connected to the computer. This is how we could record our results. Also attached to the resistor and computer was a voltmeter. We observed from our graphs that as voltage increased, so did the number of amperes, which is the unit for electric current. Since everyone in my group had taken physics before, we were able to get through the lab pretty quickly because we were all knowledgeable about current and voltage already.

After the lab, we had lunch, which was followed by our second lecture. Unlike last week, we continued discussing the same subject, as oppose to something completely different than the morning lecture. We discussed how voltage drops over the distance it travels, but current does not. We then went into the lab to prove it. We used the same batteries, voltmeter, and wires but this time we attached it all to Play-Doh so we could stretch the substance that the volts had to travel across. We proved what we were told in the lecture, again fairly quickly because this was nothing new for my group, and observed that it was primarily distance that affected voltage drop. Of course, there are other factors that come into play, but that was the major one in this experiment. I have a good feeling about our lab group because we are already working very well as a team.

Craig (another of our TAs) helps us configure the data collection software
Michael and Lindsay watch the computer track our data

After class, I walked back to the dorms with Onur. We went our separate ways for the time being and I relaxed in my room for a while. Brian had gone to the gym, so I had the dorm room to myself. Since there was a lull in my group’s activity, I decided to take advantage of it and do some laundry. Later, we all met up again for dinner. Unfortunately, the commons were packed and we had to squeeze seven people into one table where there would usually be only four. Needless to say, it was quite cramped. After dinner, we played a massive ultimate Frisbee game. Although we were losing for the majority of the game, we called last goal wins and we were able to score. Fred, Alison, Onur, Richard, and I all went to 7-11 for a slurpee afterwards to cool off (and for Fred, Onur, and I to celebrate our victory). Afterwards, we all headed back to our respective dorms. I did the remainder of my laundry and then Brian and I completed the new surveys that were posted for some of the labs from last week.

Now my Monday is coming to a close. Ordinarily, one would expect Mondays to be dreadful because of the start of a busy week right after a relaxing weekend. Today was certainly not the case. I had fun practically all day today and I definitely did not have a case of the Mondays. On that note, I will sign off so I can enjoy the remainder of my evening and then sleep at a reasonable hour.