Unit 6 Blog Reflection

The first thing we learned about in this unit was charges and polarization. The first formula we learned was coulomb's law, which is used to find the force of a charge (F=k(q1q2/d2). Distance and force have a relationship where if the distance is doubled, the force will be 1/4. We learned the 3 different ways that an object can be charged; induction, friction, and contact. Induction is when a neutral object is charged by a negative object without actually touching (as seen in picture above). Friction is charging objects by rubbing them together, and contact and where a charged object transfers it's charge to another object. A big question we answered in this section was; why does a balloon stick to the wall after being rubbed on one's hair? Being one of the longer problems, I was worried at first but it doesn't seem as bad once you start learning the steps. We learned that the balloon steals the electrons from your hair by friction (makes it negatively charged), and then the wall polarizes as it gets closer to the wall. This means the protons move closer to the balloon than the electrons do. From coulomb's law, we can see that the force between the attractive force is greater than the attractive force, so the balloon sticks to the wall.

The next topic we learned about was electric fields. The formula corresponding to electric fields is E=f/q (Force of electric field). The lines in a electric field represent the strength of the field; the closer together they are they stronger they are. One question I had trouble with was; a positively charged particle is in an electric field and moves the left while increasing velocity. The question asks if the field is caused by a positive or a negative charge. This is tricky because it could be positive, negative, or both. The next thing we touched on was electric shielding. We learned that most electronics have a hard metal shell because it protects the interior from being broken by even one small charge that could come into contact with it. The shielding makes it so that there is no net charge on anything inside the box.

One of the main questions when learning about electric potential was; why is it that when a bird stands on one end of a power line it doesn't get harmed but it gets harmed when touching both ends? The answer to this question is quite simple. When the bird is only touching one end of the power line, the circuit is not complete, so no current will flow through the bird. However, when the bird touches both ends of the power line, the circuit is complete and current can flow through. Also, when the bird is touching both ends there is a potential difference and the bird will be harmed. Potential difference is just voltage, the difference between two currents. A capacitor is a device that stores current so that it can all be released in a short period of time, and then it must recharge. This is why a camera flash has to recharge after taking a picture. 

Ohm's law (V=IR) and electric potential difference were next. Ohm's law is voltage=current x resistance. I already went over potential difference a little bit, but it is just voltage. Voltage =joules/coloumb, also (change)PE/q.

The next things we learned about were types of current, source of electrons, and power. The two types of current are direct and alternating current. DC flows in one direction (ex- battery), and AC flows back and forth (ex- generator). We learned that the electrons are actually already in the lightbulb when it is turned on, or that the electrons are already in your body when you get shocked by an electric fence. The equation for this section is Power=(current)(voltage). This is used a lot in problems along with the previous equations.

Lastly, we learned about parallel and series circuits. Parallel circuits are wired in separate branches so that if one bulb goes out, the others don't. In a series, they are all wired together in one strand so if one goes out, they all go out. In a series, the resistance adds, voltage adds, and current stays the same. For parallel circuits, resistance will be cut in half, voltage will always be the same, and current adds. Are most homes wired in parallel or series? This was a common question we had, and the answer is parallel because if one bulb/appliance goes out, then the others will still work. A fuse is a device that limits the amount of current that can flow through at any given point. This prevents overloading of current because if it does overload, a wire in the fuse will melt and it will protect the appliances because it is wired in series. 

This was a very long and detailed unit. I had trouble remembering all of the specific formulas for each section, as well as the specific details about each thing we covered. However, I had fun actually learning all of these common things about electricity that I can now use to impress my family and other friends. I feel pretty well prepared for the test, after writing this blog post, as well as studying my notes and quizzes. I hope to ask more questions in class particularly for the quizzes we take.

Types of Current Resource

      This very well animated and pleasant video explains the difference between direct current and alternating current, as well as explaining some history of energy and also explains a better way to use this current.
      I found that this video helped me understand both ac and dc current, as well as the difference between them. It explained that ac current was more commonly used and was more efficient to supply certain machines, but dc current also has it's advantages.