On Resistance and Resistors

For the first time of the semester, Mac and I were late in Physics 102.1. We had to finish the paper and make the final touches so that it would be great, but it seemed that time eluded for me and my group mate. Being tardy was quite saddening because of one reason stated later in the blog, but at least it imposed on my mind the mentality that I should NEVER be late again for 102.1.

So, for the aforementioned reason, when Mac and I entered the classroom, class had already begun and two questions in our prelab quiz were already given out. When I found out about that, I panicked because two questions in, the thoughts of failing the quiz lingered in my mind. I am not good at circuitry, and even if I studied the snippets of info on resistance in our guide sheet, I don't think I "got" what I had to know for the quiz. Thank God Sir Baldo made the quiz do-able. I only managed to get a 6/10 because I exchanged the relationship between I(total) and I(in the circuit) between series and parallel circuits. These activities (and attendance etc.) constitute 5% of our grade, so I need to up my game when it comes to these quizzes to get a decent mark... So no more being late for me!:D

The experiment this meeting was basically a compilation of "mini" experiments focused on the concepts of resistance, and consequently, resistors. Resistance is basically the ratio between voltage and current, as stated in Ohm's Law R=V/I, or in layman's terms, the measure of opposition to an electric current. Resistors, on the other hand, are devices that provide resistance to a circuit. The resistance of a sample (resistor included) is given by the equation:

R=pL/A,

where: R= resistance, p= resistivity, L=length of sample, A=cross sectional area

It was also stated that resistivity is temperature dependent. That is, at higher temperatures, resistivity increases, thus, the resistance of a sample increases.

I am not going to go into the details of the experiments that we conducted but simply give a breeze-through of what we did and what I thought about them.

The first thing we did was to measure the resistance of ceramic resistors via their bands and comparing it with the values that we got when we measure their resistance via an ohmmeter. This activity was very easy because it just required basic reading skills and simple arithmetic. To add to that, we did this in High School, which I really can't say regarding the other activities that we performed.

The second thing was finding out the schematic diagram of a resistance box. Initially, we thought that the circuit was simply a series because removing we didn't really understand how the mechanism worked. After consulting with Sir, we found out that removing the plugs actually increased the resistance and thereby there were resistors looped around each plug. It was very confusing for me because my knowledge on circuits is rusty. And the next activities just proved that more.

The third and fourth things were to find out the maximum resistance of a rheostat and a variable resistor. Initially, we thought that the rheostat increased its resistance with increased force of push.Regarding the variable resistor, we had no idea. Again, with consultation from Sir, we found out that the position of the sliding thing on the rheostat dictated the resistance because it served as a shortcut for the current to get to the other side. For the variable resistor, the same idea was concerned, though it was still confusing for me.

The fifth thing was measuring the resistance of two resistors connected in series and in parallel. This activity made use of a breadboard, and it was the very first time I've ever seen something like it. I was O_O when I saw it because I didn't know such a thing existed in this world. So, we put the resistors on the breadboard and took their resistance. We, then, solved the theoretical resistance using the bands and Ohm's Law. There was little percent error associated but they were small enough to be ignored.

The last thing that we did was circuit analysis for both ohmic and non-ohmic cases. Here, we made use of a power supply to give out voltage and an ammeter to take the current reading.For the ohmic case, we just made use of a ceramic resistor. For the non-ohmic case, a tungsten lightbulb. The obvious difference between the two cases is the pattern of the data. For the ohmic case, it was very much linear, but for the non-ohmic, the pattern was a bit eccentric but the trend was also increasing.

Admittedly, I wasn't really that useful this meeting because of my lack of knowledge on the topic. I know that it's my responsibility to know about the subject matter beforehand, but this week was very busy for me to fully prepare. To add to that, our Lecture class isn't really helpful at all because the lessons there are far behind the subject matter in Lab. It could possibly be an advantage because it implies that I would be prepared for the future topics in Lecture because we have already taken up in class.

As time goes on, I am beginning to realize that I am more of a mathematician than a physicist. It's very hard for me to grasp the concepts of electromagnetism because I can't imagine stuff that well, but numbers and equations make sense to me. Still, I want to continue on with Physics because maybe I haven't really exerted that much yet to "get" the topics. I think I can succeed if I try harder... And that is I being optimistic.