Unit 7 Reflection

 In this unit I have learned about charges, magnetic fields, electric fields, magnetism, magnetic poles, electromagnetic induction, generators, transformers, and how motors work. 

   The most important thing you need to know about charges is that the main source of magnetism is moving charges. All charges have electric fields in them, but only moving charges have both magnetic and electric fields. All objects have something called a domain. A magnetic domain is the direction in which the electrons in a magnetic field are going. When the electrons are all going in different directions, the object that contains the magnetic field is not magnetized. When they are all going in the same direction, however, there are poles which means that the object is magnetized. Magnetic fields flow from south to north. This means, that inside the magnet, the electrons flow upwards. Outside of the magnet, however, the magnetic field lines are the opposite. They flow from north to south. 

     The magnetic field of the earth is the opposite of what you think it is. We call the pole near antarctica the south pole and the pole where "santa claus" supposedly lives the north pole. It is true, these are the correct names of the magnetic field lines. However, the actual "magnet" that is inside the earth has the north pole at Antarctica and the south pole near santa claus. The reason that this is the way it is is because we only feel the force of the magnetic field lines around the magnet, not the magnet field inside the magnet itself. 

     Have you ever stuck a paper clip to a magnet, and wondered why it sticked? Paper clips are not magnetic, however, there is a way to magnetize them. A paperclips electrons are all flowing in different directions. The magnetic field of a magnet, however, pulls the magnetic domain of the paper clip towards its north pole when the paper clip is touched to the magnet. Because the magnets and the paper clips domain are in the same direction, the electrons are all flowing north. Therefore, the paper clip sticks and becomes magnetized. 

     When a charged particle is perpendicular to a magnetic field, the field repels it with maximum force. When a charged particle is parallel to a magnetic field, however, the particle joins the field without feeling a force. The easiest way to think about this is to think about the earths magnetic field and cosmic rays. Most everyone knows that the people who live on the poles are more susceptible to diseases caused by contact with cosmic rays. This is because the particles are parallel with the magnetic fields at these poles, and therefore feel no force (meaning have no trouble) entering the magnetic field of the earth.

      Electromagnetic induction is simply the process of putting a magnet through or around a series of loops of wire to generate a current or induce a voltage. The way that it works is, when you move a magnet over a wire, it changes the magnetic fields of the loops of wire and this change induces a voltage which causes a current. Believe it or not, this concept is used in our everyday lives. A car is a magnet, and the pavement has wires underneath, and this is how stop lights know if a car is waiting. Your credit card has magnets, and the machine has wires, and that is how stores know what your credit card number is. 

    Generators use electromagnetic induction to induce a voltage and create a current. They use mechanical energy in and get electrical energy out. This is because they simply have to crank something which moves magnets over a coil of wires and this movement causes a change in the magnetic field which causes a current.

     Motors are the opposite of generators, because you put electrical energy in and get mechanical energy out. We made a motor in class. We did this by using the concept of a motor and applying it to a battery, a coil of wire, two paper clips, a magnet, and two rubber bands. We did this by first bending the paper clips to make them capbaple of holding the coil of wire above both the batter and the magnet, and touching both sides of the batter in order to be able to carry the current to the wire. Then we wrapped rubber bands around the battery so that the paper clips would stay. Next, we put the magnet on the battery on the top in the middle. After that, we did the most important part. We wrapped the wire into an ovular coil that had about one inch of extra wire on each side. Then, we scraped the top (and only the top) of both wires. The scraping part is probably the most important part of the whole motor. This is because when the wire is carrying current, the magnetic field of the wire changes because of the magnet, and the electrons in the wire feel a force. The force is the greatest force possible because the coil of wire is perpendicular to the magnetic field of the magnet. This force causes a torque, which causes the coil to spin. Because the wire does not get current at all sides, and only on top, this happens over and over again. Then, you can attach a fan blade, the blade of a blender, or even wheels. This is how all motors work. Seems pretty simple, doesn’t it?

     The next and last thing we learned about was probably also the most complicated. It is a thing called transformers, and like all the other things we have learned about in this unit, it is used in our everyday lives. Transformers are simply a large coil of wires and a small coil of wires that, depending on which size is first, can either increase or decrease the voltage given to an appliance or a house. Transformers can also be used for computers, cell phone charges and many other appliances. Transformers use alternating current in order to change the voltage in the ways needed. They would not work with direct current. There are many transformers in the power lines to our houses. They have high voltage so that when they give power to our house, it is easier to reduce the voltage and increase the current. The way you figure out how many loops or volts are in the primary or secondary coil of wires is through the equation primary # of loops/primary voltage= secondary # of loops/secondary voltage.
     What I have found difficult about what we have studied is all the different points you have to make when answering each question. I overcame these difficulties by practicing answering each question a lot of times and thinking about the different concepts in relation to each other. My problem-solving skills and effort this unit have been pretty good over all. I have done all my homework and tried to study for each quiz that we had. I think my groups podcast this unit was one of our bet and we all collaborated really well with each other. My goals for the net unit is to try to rely less on what we learn in class and I plan to achieve this by paying more attention to the reading.
     I can make tons of connections to the real world from this unit because everything we studied can be connected to our everyday lives. Credit cards, car motors, security at airports, and even stop lights can all be connected back to these physics concepts. 

My Mini Motor

We created a motor in class using only a long piece of copper wire, a battery, two paper clips, and a magnet. In order to understand how it works, you must first know the function of each part of this motor. The battery was used because it supplies current, the coil of wire was used in order to carry the current, the paperclips were used to support the coil and carry the current, and the magnet was used to pull the wire coil.
     The first thing you need to do is attach the magnet to the battery and bend the paperclips in a way to hold the wire. Then you attach the paperclips to each end of the battery and tie a rubber band around it so that they stay attached. Then you take the long coil of wire and wrap it in an oval, making sure that the sides are parallel and that it is tightly wrapped. You also have to leave about an inch on each side so that the paperclips can hold the coil up. In order for the motor to actually be able to power something, you must take a sharp razor and scrape the wire until you see the silver part. A very key part of this is that you can not  scrape more than one side of the wire. If the motor is scraped all the way around, it will not work. Therefore you can only scrape the wire in one place on both sides. I will explain why later.
     The reason that this motor works is because of the magnetic field created by the current through the wire and the magnet. The magnet is facing up which means that the magnetic field it creates is running from north to south outside the magnet. The wire is perpendicular to this magnetic field, therefore when there is current through the wire there is a maximum force applied to the wire. Because the wire is attracted to this downward force, it is pulled in a direction that is towards the magnet. If you had scraped the entire circumference of the wire, the wire would constantly have a current going through it and therefore stay in a position where it is being pulled towards the wire. However, because you only scraped one part of the wire, the coil is pulled towards the magnet while it has current through it. This creates a torque. Then, once the part that you scraped is no longer touching the paperclips, the force and torque of the current being perpendicular to the magnetic field causes the coil to be pulled all the way back around. Then, the process repeats. Now, you have a motor!!
There are many things you can do now to use this motor. You could attached a small fan, the blades on a blender, and even a small motor cars wheel's! Really anything that spins that needs energy in order to move and be used now, and that's how motors work!

Magnetism Recourse

This video combines two different things that we have learned about; magnetism and induction. Using the example of a flashlight that works without batteries, it explains how you can create enough of a current using only a magnet and a wire to power this flashlight. You do this by shaking the magnet up and down, so that the electrons in the wire create a current that powers the bulb.

Unit 6 Pic

We learned about a lot of different things that can relate to this lightbulb. First of all, the light is off. When you turn the switch on the back, the circuit closes and tells the electrons inside the wire to start moving, creating current. The type of current that runs through this lightbulb is alternating current, which means the electrons are moving back and forth to create current. In order to prevent a fire from the energy that is converted to heat in the wires and not used in the filament of the lightbulb, there is a fuse right behind the plug where I plugged this light in. That fuse is a glass tube with a small metal bar through the center. When the wire gets too hot, the wire inside the glass tube breaks which breaks the circuit, even if the light's switch is on.

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.