On the First Meeting: Physics 103.1

Now that Physics lab meetings are on Mondays for this sem, I don’t think I’m going to be as stressed as I was last sem. I think that it is a good idea. Anyways, let me narrate what transpired on our first meeting.

The first Physics 103.1 meeting was quite “chill”, for lack of a better word. We didn’t perform any experiment or any hectic task. What happened, though, was Sir Baldo telling us the new things in store for us--- the experiment reporting (in lieu of the quizzes we had last semester) and the consequences for late submissions. Also, he shared to us some info about our lecture professors.

This was also the meeting where we finalized the groupings for the experiments. For Physics 103, my groupmates are Mac Aydinan, Reggie Bernardo and Julia Negre. Overall, I think that it is an excellent group. I don’t think communication is going to be a problem at all.

I’m quite excited for Physics 103.1, primarily because there are no circuits (which I hate) involved in this lab class (I think).

On Optics and Ray Box Experiments

Our first Physics 103.1 experiment dealt on a very interesting topic- Optics. I, for one, was quite excited about it because I didn’t really have much exposure to said topic in the past and I was enthusiastic to learn about it. After receiving the instructions and data sheet from Sir Baldo, my mouth dropped because of the sheer length of the experiment. It was EXCRUCIATINGLY long- composed of six “mini” experiments. Topics included color addition (where we added RGB colors using a ray box), refraction (where we learned that it was merely the bending of light and that it governed a principle called Snell’s law), reflection (where we twirled a mirror around to see what would happen to the rays hitting it), total internal reflection and the determination of the index of refraction using Snell’s law. Overall, the experiment was very tiring. Even for a group of 4, the experiment took a whole meeting to accomplish.

The first meeting was quite a “new world” for me-- well it’s to be expected coming from Physics 102.1 which was all about electric circuits. Well, it’s a sign of relief because I never really warmed up to it.

On the Investigative Project

We finally (again, FINALLY) finished the formal report and passed it to Sir. It was one of the most difficult things to do this sem, and passing it removed a big chunk of problems off my back.

With all experiments done, we now set our focus on the investigative project, which our group decided on to be the gold leaf experiment, an experiment that displays the wonders of Coulomb's Law and induction.

Compared to the other groups' projects, our experiment seemed to be relatively easy. That is, we were able to finish doing it in one very short session outside class.

Hmm. What more? I think that's about it for this post. I'll tell more about the gold leaf experiment once we've done the paper. It's the homestretch, that is, Physics 102.1 is almost over. I have to get ready for the Practical Exam, which I'm quite nervous about.

On Resonance in Series RLC Circuits, Part 2

This experiment is the experiment that we would make a formal report of. And I must say, I'm not that enthusiastic about it. Trying to make the lab notebook was almost impossible for me and Mac, maybe because we were kind of rushing to finish it to reach the "submission", but ultimately we gave up due to no prior understanding of AC, lack of time, hunger and "O_O". Unfulfilled and defeated, we went home...

Well, that was last Wednesday.

So, Thursday came and, still, we have not finished the lab notebook. And to add to that, we have not even started the formal report, which was due on that day too. So, it was literally hell on earth that day. I was ready to give up and drop out of college, but when we arrived, we realized that that meeting was not the submission of both notebook and FR, it was next week. That Thursday was dedicated for the other groups to finish the experiment. When those words began to process in my head, it was like an early Christmas for me. School has been very very difficult and tiring and excruciatingly sad for me the last couple of weeks due to the landslide of things to do and low grades, and this "moving" of the deadline was purely good news that was something nice to hear.

Yey. So, now, we really have to work hard on the formal report.:D

On Resonance in Series RLC Circuits

RLC Circuits are really complicated. That was the first thing that popped into my mind when Sir Baldo began discussing RLC Circuits, a circuit involving an AC source, a resistor, inductor and capacitor. As opposed to the topics that we have discussed for the past 6 experiments, the treatment for this one was more mathematically rigorous.

Anyways, at least we did not have a quiz that meeting, due to the fact that lack of time translated to lack of postlab quiz, so a take-home quiz was given to us.

The lecture that meeting was long, I think the longest it has ever been. It was understandable, though, because there are a lot of things that are needed to be tackled to fully describe an AC circuit. Since the voltage provided by an AC source is not constant (unlike DC), the current is not constant too, so normal methods for DC circuit analysis cannot be applied. Here, tools such as phasor diagrams and wave functions (sines and cosines) are used. It's a lot more difficult than DC. But weirdly, it looked a bit more appealing to me than DC. Still, I do not get AC that much because we have yet to tackle it in lecture class (wait, I don't think lecture class is not much help either), or err I have yet to read about it in the textbook. Another new circuit device introduced in class is the inductor, which by what I understood is a device that resists large changes in current by inducing an emf (thus a current) opposite the large change in current. Reactance (X) was also introduced. It was said to be the opposition of a circuit element to a change of electric current or voltage by the capacitor or inductor. Also, impedance (Z) was discussed. In an AC circuit, it acts as the "total resistance", and it can be plugged into Ohm's Law. Impedance, in terms of reactance of the inductor and capacitor, and resistance of the resistor, is:

Resonance of the series RLC circuit was the main thing that was the subject of the experiment. At resonance, the maximum current is obtained, and the frequency that corresponds to resonance is called, surprise, resonance frequency. Also, at resonance, the equivalence of inductive reactance and capacitive reactance is observed, and, due to this, the impedance is at a minimum.

The experiment was quite easy, as opposed to the concepts it showed. Basically, what we had to do was adjust the frequency of an AC source output and observe what happened to the voltage across the source, the capacitor, the inductor, the resistor, and the inductor-capacitor, and also the current across the circuit. We obtained the frequency where maximum current was obtained and called this the resonance frequency. We did this procedure with 1 capacitor, 1 inductor, and 2 resistors, one at a time.

We made use of the whole period and extended a bit, showing how time-demanding the experiment this meeting was. That was basically it for that meeting.

So for my thoughts: This was the first time I was introduced to AC circuits in my life, and I must say, I am a bit confused about it.:S As the semester progresses and we dig deeper into the world of electromagnetism, I get more and more "O_O" (I have no word for it, so I present a face). I really don't think that electromagnetism is my niche in the physics world, mainly because I can't really say I'm excellent at it and that much enthusiastic about it. All I can give is hard work and perseverance, and I hope that it pays off in the end.

On Electromagnetic Induction

Ok. This might have been the worst possible meeting to be late, and unfortunately, my friend Mac and I were. Because we had to finish our summary report, we were around ~25 minutes late, and the post-experiment quiz was almost over. Thank God Sir was kind enough to let us answer the whole quiz, but, still, I think that my grade in that quiz is low. I was quite clueless during the quiz, with sweat dripping because we were running before we entered the classroom. I just hope that I passed the quiz.

What's done is done, so let's move on.

Our experiment this meeting was all about electromagnetic induction. What this phenomenon means is that changing the magnetic field around a wire induces a current and emf in it. By Faraday's Law, this induced emf is equal to the negative time derivative of magnetic flux. By Lenz Law, we can note that the direction of the induced emf or current is in the direction opposite the cause of it. Therefore, if a magnet (N pole facing the coil) is put nearer to the coil, an emf and current will be induced in the counterclockwise direction, since the coil will resist the magnetic field on it due to the magnet by producing an upward magnetic field itself.

The experiment proper was quite short, because it only involved one set-up (solenoid) with different 'twists'.

This meeting introduced us, physics students, to a new measuring device ---- the GALVANOMETER. From wikipedia, a galvanometer is a type of ammeter that produces a rotary deflection of some type of pointer in response to current flowing through its coil. Using the galvanometer was the first part of the experiment. Here, I also learned (from the handout) that humans are considered large resistors. :O

We, then, looked at the effects of probing a moving magnet at the hollow part of the solenoid. It was observed that the faster the magnet was "swiped", the higher the magnitude of the deflection on the galvanometer. When it was put into the solenoid, the deflection was to the right. When it was pulled out, the deflection was to the left.

We, then, put different metals (iron, copper, aluminum) on the hollow part of the solenoid. We saw how the magnets affected the deflections on the galvanometer, and I think that it has something to do with the types of magnet because each of which was of a different type (ferromagnet; diamagnet; paramagnet).

Lastly, we looked at the effects of putting a smaller solenoid in the middle of the solenoid, and withdrawing the smaller solenoid a centimeter at a time until it was completely outside. This was the part that was quite a source of confusion because the procedure dictated that we had to start at the point when the smaller solenoid was completely inside the solenoid. There was some space between the two solenoids that was not accounted for, but we figured it out.

This experiment was relatively easy because it was quite straightforward. Compared to the past experiments that we had, this was one of the quickest to be accomplished.

Lesson learned today: don't be late. I want to repeat it to myself. Don't be late.

On the Sources of Magnetic Fields

The topic this meeting is far far ahead of the topics that we have in Lecture class, so everything was quite new to me (but thinking about it, I don't think I'd learn anything in Lecture class if we discussed this :|). So basically, this meeting was all about the sources of magnetic fields, of which there are a number of.

The first source is permanent magnets, or the objects that naturally have a magnetic field associated with them. Basically that's it for permanent magnets.

The second source is the motion of charged particles, which is given by the equation:

where B=magnetic field vector, v=velocity vector, mu-knot=permeability of free space, q=charge of the moving particle, r=unit vector from position of particle to point where B is measured

This complicated equation basically says that the magnetic field is the cross product of the velocity and position vector wrt to where it is being measured times a constant given by the other terms. This means that there is no magnetic field when the velocity and position vectors lie on the same line (cross product is 0) while it is a maximum when the two vectors are perpendicular.

An extension of this source of magnetic fields is a current carrying wire. I won't put the equation anymore because I can't find a picture of it in Google, but I would say that the equation is quite similar in form to the one stated above.

Another source is a very long solenoid. When I first heard of this word, I was quite clueless of what it is. I previously heard of it in Physics 111 when we were discussing the divergence of a vector field. It was said that a solenoidal vector field is one that has 0 divergence at all points. I had no idea of what it meant, and still no idea at present. :| What I do know is how a solenoid looks like. It's basically a wire curled up to resemble a compressed slinky. This source of magnetic field also has an equation associated with it. Here:

Okay, I now want to talk about the experiment that we performed. Just like the other experiments that we had, this experiment is also a series of 'mini' experiments about the sources of magnetic fields.

The first mini experiment that we performed was measuring the magnetic field at different points around a permanent magnet (horseshoe and bar) using a magnetic field sensor and labquest. Honestly speaking, this part was quite arduous because the measurements were quite erratic and we had to take a LOT of measurements.

Then, the next thing that we did was to measure the magnetic field from the center of a horseshoe to the outside part of the horseshoe. Okay, that was quite confusing. Basically, we measured the magnetic field as a function of distance from the horseshoe.

We, then, proceeded to perform the next mini experiment. Here, we made use of iron fillings placed on top of a folder. Under the folder, a horseshoe magnet was used, and the iron fillings aligned themselves according to the magnetic field produced by the magnet. It was quite cool because it was like magic.

We were supposed to do Oersted's experiment. Well, actually, we did but it failed. So we had to scrap it off from the procedures list.

Then, we did the final mini experiment, which was to measure magnetic field outside a solenoid which carried a current. We, then, implemented different core materials and looked at how it affected the magnetic field.

... So that's all that we did this meeting.

The experiment was very long and tiring. We were there by 1 and ended at 4, making use of the full 3 hours this meeting. Initially, I thought that the experiment would be fast. But, boy, I was wrong. I haven't fully grasped the concepts of magnetic fields, so I don't know if our data makes any sense. Well, hopefully they do.:))

It's amazing how people (physicists) discovered how magnetic fields work, and even derived equations that explain how they occur. I'd never had known any of these if I didn't enter Physics.

I was also amazed by the device Labquest. I want one for my own.:D