On Heat Transfer

The last experiment of Physics 103.1 was all about heat transfer, particularly the three processes involved: conduction, convection and radiation. Basically, we did two experiments, the first of which was a test to see if the color of the container of a fluid would have an impact on the rate of cooling of the enclosed fluid. For this part, we compared black and white bottles. The patterns we obtained for both bottles were more or less the same: both were exponential functions with approximately the same slope. This agrees with theoretical knowledge since heat transfer in the set-up was through conduction via the walls. The color of the containers do not really factor in.

In the second part of the experiment, we looked at the effect of the color of a fluid's container on the rate of heating of the enclosed fluid. We used a lamp to induce heat transfer by radiation. In contrast to the graph of cooling, the graph of heating was a straight line.

This last experiment was quite short, similar to the other thermo experiments. Dealing with the bottles was quite nice since the tools remind me of Chem 16 days.

On the Gas Laws

The experiment this week focused on two simple equations that we encountered in our Chemistry classes: Boyle’s law and Charles’ law. The first states that, with temperature constant, the product of a gas’ pressure and volume at any point in time is a constant. The second states that, with pressure constant, volume divided by the temperature is a constant.

We were tasked to demonstrate the potency of these two laws using a syringe and heat engine apparatus. For Boyle’s law, we connected the syringe to the pressure sensor and manipulated the volume of the syringe by pressing down. We took the pressure reading and got P*V. Theoretically, P*V should be a constant but the measurements we obtained were not. We blame this error on the syringe-sensor interface. Since the interface was not secured, gas might have leaked out. For Charles’ law, we put the heat engine on its side and connected it to the air chamber can placed on a hot bath. We then cooled the temperature by constantly adding ice. We obtained V/t and saw that this also did not equal a constant. The error might have been due to leakage and improper V-t measurement.

On the Heat Engine

A heat engine is a device that converts thermal energy into other forms of energy. With that in mind, we were tasked to demonstrate the cycle of motion of a mass lifter heat engine composed of a piston attached to a system and an air chamber can.

A discussion of how heat engines work is not provided here. Suffice it to say, the engine cycle consists of two parts: the isobaric part (constant pressure) and the adiabatic part (no heat flow). These parts correspond to the addition/removal of mass on the piston, and the exposure of the air can to hot/cold temperature, respectively.

Initially, I was quite clueless with what to do with the piston apparatus, which costs P35,000 as repeated quite often by the person handling the equipment, since it was the first time for me to handle the device. It was not intuitive to me why the piston shifted height upon exposure of the air can to hot/cold temperature . I really had to think it over after the experiment. These deterrents caused me to be not much of a help with the procedural part of the experiment this week.

On the Freezing and Melting Point of Water

After a long hiatus, our Physics 103.1 lab resumed last Monday. What greeted us back was a relatively easy and quite fun experiment that dealt with the phase changes of water: freezing and melting. This entailed that we would be dealing with ice (which was fun to munch on) since we had to freeze tap water and monitor the temperature changes accompanying it. After creating ice, we boiled a cup of water and placed our newly frozen ice near the warm water. Similar to the first part, we measured the temperature along the way until the ice melted. 

Our results showed that the freezing and melting points were one and the same- that is, 0 deg celsius. Also, the plot of temperature vs time for the freezing part fitted an exponential graph with negative argument while that of the melting part had a constant part and an exponential part. We encountered a bit of a problem with freezing the ice because we forgot to put salt (which causes freezing point depression on the surrounding water used to freeze the ice). But otherwise, it was smooth sailing.

On Resonance and Sound

In contrast to our experiment last meeting (Calorimetry), we performed an experiment regarding waves this week. Specifically, we performed an experiment which demonstrated resonance, the increase in amplitude of vibration of a body due to the constructive interference of the driving force of the vibration’s frequency and the body’s characteristic frequency of vibration.

Using a resonance “tube” filled with water and a speaker of constant frequency on top of the tube, we looked for the water levels wherein the sound volume was at a maximum. These water levels correspond to the length of the tube that allowed standing waves to be set-up. Also, at these water levels, resonance was observed. By getting the average of the difference between the distance where resonance was observed, we were able to obtain the wavelength using ΔL=½λ. Finally, using v=fλ, we obtained the speed of sound in the tube.

The experiment was quite difficult because it required us to hold the speaker manually above the tube. It was tiring so we took turns doing it. Also, water from the tube unfortunately spilled on the floor which caused quite a mess. Apart from these, I thoroughly enjoyed the experiment because we had good group dynamics.

On Heat and Calorimetry

Entering the 103.1 lab, I saw a gas stove set up. Asking what it for, I found out that we would be performing an experiment on Thermodynamics.

I consider Thermodynamics to be my favourite subject in our General Chemistry courses (16 and 17). Unfortunately, I have forgotten quite a deal on the said subject, so it was nice to rekindle my interest in thermodynamics by performing a simple calorimetry experiment this meeting.

Basically, what we did was mix hot and cold water together and measure the enthalpy change (ΔH=mcΔT) to see that the heat lost by the hot water and the heat gained by the cold water were equal. It was quite an easy experiment, though numerous little niggles cost us time. For one, the balance used to measure the mass of the calorimeter was in the other room so we had to go back and forth between rooms (though this was remedied eventually), and a short brownout occurred which we had to wait out to be able to use the balance.

Overall, the experiment was quite a simple task to perform. Compared to the experiments in 102.1, this experiment was a walk in the park.

On Light Intensity

The second experiment we performed was all about light intensity. To cut the story short, it was a quick experiment, not taking up more than 30 minutes. It was a relatively easy task--- we simply measured the light intensity from a light source and a laser at different distances from the light source using a light sensor connected to labquest.

From the graph of light intensity vs. distance from light source, we observed an inverse square law; that is, the light intensity is inversely proportional to the square of the distance from the light source. This conclusion was obtained using data from the light source (not laser). The data we got from the laser showed that light intensity was constant even at great distances. It could probably be the case that the intensity from the laser was so high that very great distances would be called for to see the inverse square law.

We encountered minimal error, if none. I think our group had good dynamics because we finished the experiment in record time. I hope that the next experiments are going to be as easy as this, so that we would always finish ahead of time. :D

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

On Kirchoff's Rules and Capacitors, the Return

The whole meeting this week was dedicated to answering a relatively long quiz about our previous two experiments.

The quiz was implicitly divided into two parts: one on Kirchoff's and the other on capacitance. The first set of items on Kirchoff's Rules were quite easy, because it just demanded from us knowledge on how to use the equations of Kirchoff's Rules. But it was a bit of a struggle for me to get the right answer because of wrong arithmetic. Roar.

The second set of items on Kirchoff's Rules required of us deeper thinking. And this is where I was sweating bullets because it was quite difficult.

The capacitance part of the exam was easy, relative to the part on Kirchoff's Rules. We were given the equations of the charge and current. The only thing that we needed to do was to plug in values. :D

Needless to say, this quiz was a challenge for me, but what made it tolerable was the fact that Mac helped me out and that Sir Baldo was there, available if help was needed.

After the exam, Sir Baldo returned to us our lab notebooks. He told us that we were given a chance to revise our not-up-to-par lab notebooks so that we would have a higher score. :D

On Trials and Tribulations

My blog post this meeting is short, primarily because we didn’t conduct an experiment.

Anyway, this meeting was dedicated solely for reviewing the coverage of our long exam (which by now is already two days past). Needless to say, the review was very useful and informative. Some selected items in our problem sets were answered live by sir, which made me go “ah” a few times because of the fact that some items were easier watching being answered than answering them myself. Sir was also kind enough to provide a copy of the answers to us. Thanks Sir! ^_^

Some thoughts on the exam:

ü The exam was excruciatingly HARD. (I don’t know if others had a hard time as well)

ü I think I failed the exam.

ü I hope the checker is generous in giving partial scores.

I guess I’m not really cut out to be someone great at electromagnetism. One exam down, three more to go. I hope I don’t fail the other exams.

On Kirchoff's Rules and Capacitors

This meeting was quite hectic because two activities were scheduled to be done by 4 pm so that we wouldn't have to perform any experiment next meeting, and we could just review for our long exam in 102, which I consider my impending doom.

Anyway, the lab meeting started with a lecture on Kirchoff's rules and Capacitors, two very new concepts for me. Because of the possible lack of time, the quiz on these topics was postponed to next next week (yey!).

So, the first topic for the lecture was Kirchoff's rules, which are basically two rules on how to simplify measuring current and voltage in a DC circuit.

The first rule, the junction rule, states that "the algebraic sum of the currents at any branch point or junction in a circuit is zero." This rule fortunately conforms to common sense, so "getting" it isn't really that hard. For example, in the situation where a junction connects three branches and two currents (I1 and I2) are flowing into the junction, th

e current flowing out of the junction is I1+I2. Basically, the junction rules says that the sum of the directed currents in a junction is equal to 0. It is, in disguise, the Law of Conservation of Charge.

The second rule, the loop rule states that "the algebraic sum of the potential differences around any complete loop in the network is zero." This is a bit more difficult to grasp qualitatively than the junction rule, nevertheless, it's still a lot easier to understand than the things we learn about in 102 and 111. To put it simply, the voltage input and output must equal zero for any loop in the circuit. After reading a bit about it in University Physics, using the loop rule seems a bit complicated when the loop involves a lot of circuit elements.

The second part of the lecture was about capacitors and capacitance, a new addition to 102.1's ever growing collection of circuit elements.

The marking C is the capacitor in the circuit, and the unit of capacitance is farads. Before going in deeper on capacitors, let me first define it. Capacitors are devices which can store charge, and capacitance is just the measure of how much charge a capacitor can store. The amount of charge stored is determined by

Q=CV

where Q=charge, C=capacitance, V=voltage

The capacitance C is given by another formula:

C=EA/d

where E=permitivity of free space, A=area of the plate of capacitor, d= distance between capacitor plates

When there is an insulator between the plates of the capacitor, the capacitance C becomes:

C=kEA/d

where k is a constant of the insulator that is very much greater than 1

We, then, described the effective capacitance in series and parallel circuits. For series, the capacitance formula is equivalent to that of the resistance formula for parallel circuits. For parallel, the formula is equivalent to that of the resistance formula for series.

The charge obtained by the capacitor and circuit current, as functions of time, was derived via integration. The formulas are:

q(t)=CV(1-1/e^(t/RC)) ----> charging (charge)

i(t)=V/(Re^(t/RC)) ----> charging (current)

q(t)=Q/e^(t/RC) ----> discharging (charge)

i(t)= -Q/RCe^(t/RC) -----> discharging (current)

Wow, those were a lot of formulas.:o

Anyway, we started doing the experiments after the lecture. The first we performed was the experiment on Capacitors. The first thing that popped into my mind when I saw the capacitors was that they seemed awfully familiar. I remember very vaguely that we handled capacitors in HS, but I do not know what we did with them.

The experiment on Capacitors was basically a string of activities that, in one way or another, displayed the wonders of capacitors. I do not want to go much into detail but as an outline, what we did are as follows:

• dissected a capacitor (which was quite difficult)
• measured the capacitor's capacitance (with the ever-powerful multimeter)
• measured the capacitance for series and parallel combinations
• made an experiment that proved the equation Q=CV
• energized a capacitor and connected it to a voltmeter that was connected to a computer and by using labpro (which was cool), graphed the time vs voltage plot

There was a lot of sources of confusion for this experiment. One of which is our lack of knowledge on capacitors. I, for one, do not know a great deal about capacitors, and I consider myself an amateur when it comes to circuits. The last mini activity was confusing because there was a lot of things involved, and the procedure stated in the activity sheet didn't really go much into detail of what we were supposed to do. Thank God Sir was there, kind enough to help us out.

Lab Pro was really cool because it not only allowed us to get the graph of time vs voltage, but it also allowed us to get a best fit curve of the graph. For the first part of the graph (charging up until the capacitor was fully charged), the graph resembled an inverse exponential function. For the second part of the graph (after turning off the power supply/ discharging the capacitor), the graph resembled a natural exponential function.

By 3:40, we were done with the Capacitor experiment. With only a few minutes left until 4:00, we had to rush the Kirchoff's Rules experiment.

Around this time, too, I saw who I thought was Mikaela Fudolig entering the room looking for our instructor. I was :O and very starstruck (Mac was too) because Mikaela Fudolig is amazing. Having that high of a graduating GWA (1.099) at a young age (16), with her course being Physics to boot, I consider her very inspiring and cool.

I digressed. So, back to the experiment. It was quite a short experiment. We just set up a circuit given a diagram and just measured the voltage, current and resistance. By using Kirchoff's rules, we then solved for the current passing through each element... actually, we didn't do the last step there because it was already past 4. So, we just did it at home.

These two quickfire experiments were quite difficult for me because it required of us to be fast workers, so that we would finish by 4. Knowing myself, my motto in these kinds of experiments is 'work slowly, but surely'. Needing to finish 2 experiments in a span of 2 hours, my motto was thrown out of the window.

It's nice to have groupmates that are very much knowledgeable on circuits. After class, I can ask things that I did not understand during the course of the meeting. For example, using the breadboard was still quite vague to me. I can ask help from Mac after class and after that, I'm enlightened quite a bit.

So, I plan to read on the topics that we have discussed and will discuss, and hopefully by next next week, I will be a master of circuits. :D

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.

On Electric Potential and Electric Field

This meeting marked the first laboratory experiment for the subject.

Prior to that, though, we had the chance to chat with our lab instructor, CK Baldo, since the Physics 72.1 class was not yet finished. I appreciate moments like these because the atmosphere during these times is light and not stressful. It also helped me ease up a bit because I was quite nervous for the experiment considering that I am not a master of electromagnetism by any means.

After that, we transferred rooms and grouped together. My group, composed of myself, Mac Aydinan and Third Garcia, I must say, has good dynamics. Mac and I were lab partners last semester in 101.1 and I think that turned out well. With regards to Third, I haven't really gotten to know him that well because this is the first time that the two of us are classmates in a small class.

Before starting with the experiment, we had a prelab quiz. I had a preconception that the prelab was about the experiment at hand, but I soon found out that my preconception was wrong. The quiz was about electromagnetism in general, zooming in on point charges and electric field. There I was, panicking, because I was unsure of all of my answers. Thankfully, I managed to get an 8/10.

The experiment this meeting is entitled Electric Potential and Electric Field. To be honest, I really do not know the formulas and specifics of these two because of my weak background in this field of study. But still, as an aspiring physicist, I have to, at the very least, familiarize myself with it and, if I am done with that, learn it by heart.

For the specifics of this activity, we had to put two electrodes(spherical and line) on two sides of an electrolytic tank (which is basically a tray filled with water). Then, we grounded one electrode and connected the other to the positive terminal of a battery. We took the voltmeter readings of both electrodes and got 0 volts and 8 volts respectively. Then, by using a probe, we plotted the equipotential lines of 1 volts to 7 volts.

I think that the goal of the experiment was to show that charged objects emit electric fields and that the shape of the objects have an effect on the electric field distribution. It also showed that the electric field lines and equipotential lines are perpendicular and the reason behind this is that to move around an equipotential line entails no work done and for this to occur, the electric field must be orthogonal to it at all instances.

I learned a lot of things from this experiment. First, I learned the notion of the electric field. All charged objects emit an electric field (which when positive is directed away from the object and when negative is directed towards the object). This vector quantity (E) is equivalent to F/q. Another term I learned is the electric potential V. This quantity is electric potential energy divided by charge and is dependent only upon location in the electric field. Around a charged body is a set of curves called equipotential lines. These curves, from their namesake, are curves that have the same potential at any point. These are also perpendicular to the electric field lines. The concept of this orthogonality is not necessarily new because we discussed the occurrence of orthogonal trajectories in Math 54.

After surviving through this first experiment, I realized that I have a LOT to learn to survive the semester. But I do think that I can make it through alive if I study hard and think optimistically.

On a Fresh Start: Physics 102.1

Fresh from the challenge that was Physics 101.1, I am, at present, thrust to a bigger and more formidable challenge.

Physics 102.1, Lab for Electromagnetism, is something I'm quite scared about primarily because I barely know anything about the subject at hand. I'm planning to take all the lessons in strides and just enjoy the ride. Que sera sera.