Coming Down the Home Stretch

Another unit has come and gone, but this one has gone on particularly long because of spring break. We took a short break about half-way through the unit, so it might cause some complications for the test tomorrow, but I guess we will see. In this unit we learned about charges, why our hair sticks up when we put on a sweater, why ser, how lightning is created, conductors, insulators, polar, coulomb's law, electric fields and shielding, electric potential energy, voltage, the different kinds of currents, why CFL's are greener than incandescent light bulbs, and why a fuse blows when multiple appliances are plugged in at the same time. To start off, we learned about charges. We know that positive charges are called protons and negative charges are called electrons. When there is an even amount of positive and negative charges in an object, then it is considered neutral. However, when there are more negative charges, the object is negative and vice versa. Opposite charges attract each other whereas like charges repel each other. There are three ways we learned to charge and object. These three ways are by direct contact, friction, or the process of induction. We use these ways to charge an object to explain why our hair stands on end when we pull a sweater over our heads. The sweater rubs against your hair and therefore steals electrons. The sweater most likely becomes negatively charged and likewise the hair most likely becomes positively charged. Because the positive charges want to repel each other, your hair stands up on end to get away from itself. Next, we learned about lightning, how it is produced, and how a lightning rod protects a house from being struck by lightning. Lightning is created when the clouds are charged through friction. The ground is positively charged, and therefore the negative charges from the clouds will attract the ground while the positive charges from the clouds will move away. The negative clouds and the positive ground will eventually attract each other so much that lightning builds up. We learned that lightning moves up and not down. Lightning rods are tall pointy tower that are on top of your house and then run along the sides of your house into the ground. The lightning is attracted to the pointy end of the lightning-rod and will therefore hit it. The energy from the lightning is then directed from the rod, down the side of the house and into the ground. Following this, we learned about conductors and insulators, polarization, and Coulomb's law. A conductor lets a charge move through it whereas an insulator stops the charge from moving. That's pretty simple, but polarization takes things up a notch. When something is "polar" it means that the charges separate and go to the opposite sides of an object. However, the object will still be neutral as long as there are the same amount of protons and electrons. Now let's apply this to using seran wrap. Seran wrap is negative. When it reaches the bowl, the negative electrons go to the wrap and the negative electrons move away. The bowl is now neutral and polar. Another law we use to describe this is Coulomb's law; this law states that the force between any two objects is inversely proportional to the distance. Therefore the farther away something is, the less the force. The equation for this is Kq1q2/d^2. Looking back at the seran wrap example we see that the distance between the attractive charges is smaller than the distance between the like, repelling charges. Thus the force will be greater between the bowl and the attractive forces will be greater than the force between the like, repelling charges and the bowl. Next, we learned about electric fields and shielding. We defined an electric shield as an area around a charge that can push or pull another charge. The negative charges will be pushed out and the positive charges will be pulled in. THe field lines of and electric field indicate how strong an electric field is; when the lines are closer together, the electric field is munch stronger. We then discussed circuit boards to move onto shielding. We learned that a circuit board needs all atoms to be in their proper place. When a negative charge is surrounded by positive charges, the negative charge will feel no force acting on it because the charges counteract each other. It doesn't matter the negative charge's position in the sphere. This is called electric shielding and this helps keep electronics safe. Next, we talked about electric potential and electric potential energy. Electric potential is also known as voltage, and is represented by PE/q; q stands for charge. The electric potential energy is the potential energy of charges. This occurs in like and unlike charges. Most importantly, we learned about the relationship between resistance, current, and voltage. Current is the energy that runs through a circuit and resistance is how easy it is for current to run through this circuit. Based on various experiments we did in a lab, we learned that current and voltage are directly related whereas resistance and current are inversely related. We show this by the equation I=V/R. Finally, we learned about DC and AC, why CFL's are greener than incandescent, and the difference between series and parallel circuits. DC stands for direct current and ac stands for alternating current. The difference between CFL's use less wattage with the same amount of brightness. Finally, we learned about series and parallel circuits. When more appliances are added to a series circuit, the resistance increases and thus the current decreases. However, in a parallel circuit, when more appliances are added, the more the current is, thus decreasing the resistance.