Voltage/Capacitance and Electric Force

Okay, so we learned in the last lovely blogpost that volts are the units of electric potential (not to be confused with electric potential energy, uh-huh.) But voltage is something entirely different. It's the amount of push you get to do something. Now, there's a specific equation to find voltage, or potential difference, in parallel plates. That formula is W=Eqd, where Work equals the product of distance, charge (coulombs) and the electric field (Newtons/coulomb). We also learned about CAPACITANCE :) which is basically short term energy storage. It stores lots and lots and lots of voltage, but not a great deal of charge. You can find this sort of thing in keyboards and touchscreens, which is why I've included a random (and probably sort of lazy) photo of my iPad notes from class. I can't really explain how it works in touchscreens, but I'm assuming its the same principles as the keyboard.

Anyhow, the plates in the keyboard work kind of like this: when you shorten the distance between the plates (aka the space between the key and the board), the voltage decreases, and sends a message to the circuits and the computer to produce whatever letter you just pressed. That is how I am able to type this post, yups. Now here's the technical portion: capacitance is measured in Farads (yes, it sounds very Middle Eastern, get over it) and the equation for it is Capacitance = Permativity of Free Space (a constant, generally air) multiplied by the area of the plates, all divided by the distance between the plates. It's a pretty easy thing to remember. :) See you next week!

Electric Potential

So this week (if today counts) we learned about electric potential energy and electric potential. First off, DO NOT GET THESE CONFUSED. Or else Da Freitas will come and eat you. Just kidding, he'll probably play you a song. Anyhoo, electric potential energy is basically another type of energy that falls in the stored energy bracket with its friends "gravitational" and "spring." To define it in a "proper manner," it is the stored potential energy of a charged object in an electric potential field. That means JOULES are your choice of unit! However, pleasepleaseplease do NOT get this confused with ELECTRIC POTENTIAL units, which are volts (aka joules per unit of charge). That makes the relationship between electric potential and electric potential energy similar to power and work, in that the latter for each relationship is just a smaller part of the first.
Now, I have a photo of the plug in the Concert Glee room where I am typing this out because we talked a lot about volts in class today. If you touch a plug like the one in the photo, you will more or less be shocked. Duh. But guess what? It's the amount of charge coming out of the plug that hurts you, not the 120 V flowing through. So, the next time you get shocked (WHY??? You're supposed to be mature/old enough to not do that...), at least you know it's the charge! :)

More about charges.

So this past week I didn't learn too much about charges... we had a sub and most people sat around playing Tetris Battle.  :)  But we did talk about electric fields and forces... kind of. We talked about electric fields... the more charge you have, the bigger the electric field. Which is kind of like the more children you have, the bigger your home should be to accomodate them. Anyhoo, the arrows in this electric field are pointing away from the charge, meaning that the field's charge is positive. On the other hand, if arrows were pointing TOWARD the charge, the charge of the field would be negative. Also, if the number of arrows on this picture were doubled, guess what? Yeah, that's right, geniuses. The charge would be doubled, too. Another thing I learned (TODAY, haha) was about electroscopes. They're these stick-figure-without-any-arms things that are electrically neutral and can change charges and move the "legs" of the stick figure when the charges are changed. Also, these electroscopes can be polarized: when charges move to create a positive side and a negative side, effectively dividing them. So, that's all, folks. I don't really have much else to go on about. Shooots :)

Charged with Excitement

Can you find good conductors and insulators in this photo? ...I can...

Happy New Year! I'm just CHARGED with excitement to be here in Physics... and yes, our newest unit is CHARGES. If we think back to Chemistry, we remember that there are three types of charges: protons, electrons, and neutrons. The other day we learned about the Charge Force Law: like charges will repel, and unlike charges attract. Therefore, ++ and -- charges go together, but when oo (neutral charges) go together, they have no effect. We also learned about conductors and insulators. Conductors may be in CHARGE of directing music, but they are also items that transfer electrons easily (and conduct heat very well.) Examples of these are metals, salts, and salt water. Insulators, on the other hand, are items that want to hold on to electrons, meaning that they stay charged longer. Examples of these are rubber, cardboard, wood, and even glass. Finally, we learned about the conservation of charge law, where in an isolated system, charge is conserved. Mr. Blake proved this law with a cloth and a stick. He rubbed the cloth to give it a charge, then threw it in the air, putting the stick near it. Every time the stick went near the cloth, the cloth repelled it, meaning that they had the same charge. And when something has the same charge, the other item doesn't get charged. The bottom line? You want to be neutral like Switzerland.