Unit 6

This unit was all about electricity. We learned about current, resistance, voltage, charge, electric fields and shielding, polarization, circuit breakers, parallel circuits, series circuits, and fuses.
    Current is measured in amperes, and can only be created if there is a difference in voltage. For example, if one side of a power unit had 70 volts of power and the other also had 70 volts, there would be no current therefore no power. This is because electrons flow from high voltage to low voltage. Voltage is measured in volts and is equal to the potential energy over the charge. When the wires conducting the current are wide and short the current flows more quickly and when the wires are thin and long the current flows more slowly. There are two different kinds of current, alternating current and direct current. All houses now a days are wired with alternating current, and only very few things (one of them being batteries) are wired with direct current. Alternating current is when the electrons in a wire move back and fourth all together to create a current. Direct current is when the electrons flow in a circle to create current. Alternating current is more popular because it is less dangerous and more efficient.
     Resistance is measured in Ohms. Resistance is used in order to lower the brightness on a light bulb or to give a device a smaller current than is using from the wall. Ohms law says that resistance is inversely proportional to current and directly proportional to voltage. Ohms law is current equals voltage over resistance, or , I(current)=V(Voltage)/R(resistance).
    Voltage, as I said earlier, is equal to the electrical potential over the charge. Difference in voltage is the only thing that can create electrical current. When a device has a large difference in voltage and you touch the wires in a way that causes the energy to go through you, you could get very hurt because a high number of electrons are flowing through your body. When you stand on a insulator, however, like a wooden chair or a carpet, it does not allow the energy to flow to the ground therefore you can not be hurt.
    There are two different types of charges, positive and negative. Positive charges have more protons than electrons and negative charges have more electrons than protons. There are three different types of ways for something neutral can be charged. Contact, friction, and induction. Contact and friction are cause by an object stealing electrons or protons from another object in order to become charged. Induction is a way to charge without contact. The reason that your hair sticks up when you take off your sweater is because your hair and the sweater rub against each other creating friction. This friction causes your hair to become positively charged and the sweater to become negatively charged. Because like charges repel each other, the protons in your hair are repelling each other causing your hair to stand up.
    Electric fields and shielding was the hardest part of the unit for me to learn. However, once I got the hang of it it became very easy. An electric field is the area around a charge that can influence another charge. Every electronic is put in a metal case because  all of the circuit boards on objects such as vcrs, play stations, phones, even ipods have an electric field around it that, if touched by another charge, could ruin the electronic for good. Metal is not a conductor, therefore the electric field inside the metal case can not be harmed and the object will never be ruined because of another charge.
    Polarization explains why plastic wrap sticks to glass bowls and why balloons stick to walls when you rub them against your head. There are two types of objects, conductors and insulators. Conductors let charges move through them, insulators stop charges from moving. Conductors are the only types of objects that can become polar. Since glass is a conductor, the friction from the plastic wrap being torn from the box causes the wrap to become charged. Since the bowl is neutral, when the wrap touches the glass it causes the like charges to repel to the other side of the bowl and the opposite charges to be attracted to the top of the bowl. According to coulombs law, which states that the force between any 2 charges is inversely proportional to the distance, the force between the top of the bowl and the wrap is greater than the force between the bottom of the bowl and the wrap, therefore it sticks. The formula for coulombs law is f(force)=q1q2(q=charge)/d^2(distance squared). An easy way to understand coulombs law is to look at it like this;
the smaller the force the bigger the distance df
and the larger the force the smaller the distance df
    Circuit breakers and fuses are used for the same purpose. The energy that voltage creates is not all used up by the device, some of it is converted to heat. The higher the current, the more heat you have. If you have too much heat you have a fire and your house burns down, and no one wants that. So, circuit breakers and fuses both make a closed circuit open when it gets to hot, but they do it in different ways. A fuse is what we learned about most, because it is what is most used. A fuse is a small metal wire inside of a glass tube that is connected to either the positive or negative side of the power source. It is placed there so that when the wire gets too hot, the metal inside the glass melts and breaks the circuit of the whole house, not just one object, therefore preventing fires throughout the whole house.
    There are two different types of circuits. Parallel circuits and series circuits. Series circuits are when every device is connected together and to one power source. In a series circuit the more devices you add the smaller the current gets and the less energy the devices in the circuit are allowed to use up. In a parallel circuit, each device completes its own circuit with the power source. So, the more devices you add the higher the current needs to be to supply each device with the right amount of power. Houses are wired in parallel, and almost nothing is wired in series.
    I found electric shielding and fuses the most difficult to learn because there is so much to remember. However, I overcame these difficulties by visualizing how they work and looking at many different kinds of examples of each in order to get the best understanding that I could.
     My problem solving skills and effort in this unit have not been as top notch as others, however I got all my homework and studied for all the quizzes and the test. I was as creative as I could of been, but my self-confidence in physics was lower than usual which made me realize that I could have definitely used more time to go over everything we had learned since it was such a big unit.
    It is very easy to make connections to the real world with this unit simply because we use tons of electricity everyday. Now I know why my computer and phone are in metal cases. I know why lights burn out when you turn them on, how my house is powered, where the electricity I use to plug in my curling iron comes from, and many other things.