Bye 102.1!

Aww. so the course is done. :(

We just finished our practical exam which was really fun (because it was answerable enough) and our creative work presentation which I think, went really well.

Soooo, I'll keep updating this blog whenever my thoughts come in place. ^_^ It was really fun remembering those experiments we did and actually realizing that I did learn something by figuring things out in the lab. I'll also miss the lax atmosphere of it. The 'just-right' class that won't make you become extremely stressed out and gives us the opportunity to figure out and discover things through observing. It was not a spoon-fed class, nor a "go-figure-it-out-we-won't-give clues" class. 

I know it's late but I haven't finished my blog to the last experimetn during the deadline, but still, I want to finish this: for self-fulfillment and future reference.

Things will never be easier in college, especially with the course I'm taking. But with these simple (not for me) things we learned, we're ready to go further.

The Experimental Two Capacitor Paradox

Yeaap! This is our creative work, but we didn't study about the question of loss of energy in connecting two capacitors (one charged, one uncharged). We just observed the change in the potentials of both components.

We already did another experiment three meetings before this idea came out. We were measuring the potential and magnetic field of a solenoid connected to an RC circuit. However, we weren't able to find significant results. For three consecutive weeks, we tried but nothing happened. On last day of 102.1 lab class, I took two capacitors from our set-up and played with it (like those little children playing with their dolls XD) and then a simple thought crossed my mind: What if an uncharged capacitor is connected to a charged one (same capacitance)? Jom and Josh thought that ideally, the one will be charged, and the other will be uncharged, and the charge will go back and forth and will be oscillating all throughout. And poof! we have a new investigatory project! Amazing right? :))

(tbc)

Resonance in Series RLC Circuits

We studied one of the most important circuits used in electronics today. It's an RLC-Circuit with an AC source. These circuits create signals that we use in tuning a radio or making a television reception clearer.

In this experiment, the RLC circuit was tested with different frequencies from the AC source (power supply that oscillates). Using a multimeter, we measured the current and voltage created on the the circuit. (I was hoping that we were going to use the oscilloscope) :(

Same as the graph above, the results were obtained. 

(tbc)

Electromagnetic Induction

Last experiment we discussed about electric currents creating magnetic fields, now, it is the otherwise. This is explained by:

This states that a change in magnetic flux creates an opposing (denoted by the negative sign, which is described by Lenz's Law) induced current. On the other hand, Lenz's Law states that the direction of any magnetic induction effect is such as to oppose the cause producing it. When the magnetic field increases, the induced current is clockwise, when the magnetic field increases, the induced current is counterclockwise.

Before the experiment, we were taught how to use a galvanometer. Its deflection tells the magnitude of the current induced and its direction. We tested it by connecting it to a power supply, and attached a resistor with large resistance. In this case, we used the human body as the resistor, which was quite amazing to know.

In this experiment, we observed the electromagnetic induction in a solenoid in three different ways:

The figure above shows induction experiments due to (A) a moving magnet (B) varying current (C) decreasing number of turns of the primary solenoid

I noticed that the deflection and magnitude readings of the galvanometer are affected by the following:

• the speed of the magnet going in and out of the solenoid and when it stops, the meter reads zero
• the reversing the polarity of the magnet also reverse the deflection of the galvanometer.
• the distance of the primary solenoid from the secondary solenoid
• turning the power supply on and off

It was a simple experiment and everything was straightforward.

Where does Magnetic Fields come from?

Our fifth activity was about sources of magnetic fields. Before I thought that these only come from those magnetic metals I used to play with and stick on the refrigerator's door. Until when we had a little experiment in Grade 6 where we wound an iron nail with copper wire and connected it to a battery. "Magically" it attracted all those small pins we had. I was twelve then, and I had no idea why they were like that. My teacher just told me that they were caused by electromagnetic forces.

Now that I'm in college, it was only then I learned that a simple current-carrying wire can create magnetic field. Through this experiment, I was able to understand the magnetic field, and its relationship with electric field.

First off, we observed the behavior of magnetic fields in natural magnets We measured the magnetic field strength of a magnet using a sensor. We found out that it is stronger on the poles than away from it. We saw something like the picture above, by putting a sheet of paper over it and sprinkling iron dust over it. Bits of iron aligned with the magnetic field lines. 

Next, we dis Oersted's experiment, wherein we connected a wire to the power source and placed a compass over it. When the switch was closed, the compass needle deflected because the current-carrying wire created a magnetic field. This phenomenon is described by Biot-Savart's Law wherein moving charged particles create magnetic field. In this case, the chraged particles moved in the conductor.

We then observed the magnetic field created by a solenoid: a coil made of varnished copper wire. We made a current run through it, making it an electromagnet. We observed the effect of the number of turns of coil with respect to the magnetic field. We noticed that the values dropped when we lessen the number of coils. This observation verifies the equation derived for solenoids, which is:

There was also an effect when different metals are inserted into the core of the solenoid

It was fun to know that magnetism doesn't only exist in permanent magnets, but also in simple wires that has current on it.

Charged!

"Ooh, so this is how a capacitor looks like!"

Experiment 4 was about Capacitors and RC Circuits. We had simple methods in doing this but very significant results were observed.

Starting off with the capacitors. They're small cylindrical (sometimes rectangular) devices with two wires of different length (the longer one is the positive and the other is negative). They kinda look like those small stuff who'll control your brain if they get inside your nose haha!

Okay. Enough with the nonsense.

The first part was that we have to "dissect" a capacitor. We thought it was easy opening a capacitor, but we were wrong. We destroyed about five or more capacitors, most of them are crushed into tiny pieces that we cannot identify what's inside. I spent most of the time trying to break one correctly, so we had to assign each member of our group the parts of the experiment. Finally, I was able to open one using a wire stripper to hammer the screw driver. And the inside of the capacitor looks like this (ceramic):

The white part is the dielectric which looks like a plastic and the grey part was the metal foil. The rolled into concentric cylinders. However, when we opened the carbon capacitor, it has cottony-like substance on it and black powder, which I think is carbon.

Off with the RC Circuits!

This part had two sub-parts: charging the capacitor and discharging the capacitor. To charge the capaciotr, we had to connect a resistor in series with the capacitor, and then make a current flow through it with a power source. We used the ever awesome Vernier LabQuest to measure the potential difference across the capacitor with respect to time. When measuring device is reading a constant voltage, we then disconnect the source and closed the RC circuit and continued the run.

After a few trials, we observed something like this:

       

From our 102 lecture class, the time constant tau, is equal to RC. This is the time taken for the charging (or discharging) current (I) to fall to ¹/e of its initial value (Io).[1] This time constant corresponds to how progressively slower the charging and the discharging is. 

[1] http://www.kpsec.freeuk.com/capacit.htm