Unit Reflection

We learned about various concepts pertaining to magnetism in this unit. First we learned about magnetism and magnetic poles. Moving charges are the source of all magnetism and groups of these moving charges are called domains. Imagine that domains were arrows, a magnet has aligned domains meaning that they are all pointed in the same direction. These aligned domains create a north and south pole that cause a magnetic field. The magnetic field goes from south to north and around the magnet back to the southern pole. The like poles repel and the unlike poles attract. This field can align domains in other objects to make them stick to the magnetic object or magnet, for example it could answer why paperclips stick to magnet.  The paperclip has domains, which are groups of moving electrons, that are unaligned and the paperclip is not magnetic. When you bring the magnet to the paperclip the magnetic field in the magnet align the domains in the paperclip and cause it to stick to the magnet. When the domains are aligned the magnet becomes polar and there is a magnetic field around it so the north pole of the paperclip is attracted to the south pole of the magnet. The earth is actually a giant magnet, however the geographical poles and the magnetic poles are different.  The geographical poles are the North Pole in the arctic and the South Pole in Antarctica. The magnetic poles of the earth are that the top is the southern pole of the earth’s magnet and the bottom is the northern pole of earth’s magnet. The way the magnetic fields of the earth form shield the earth from gamma space rays that could be cancerous. However, gamma rays can enter earths atmosphere when the gamma rays are aligned with earths magnetic field lines near the geographical north or south poles.
hNext we learned about forces on charged particles in an electric field and motors. Motors turn electrical energy into mechanical energy. We began learning this by making our own motors in class. We used a battery, magnet, rubber bands, copper wire, and two paperclips to make the motor. The battery acted as the energy source, the rubber band held the paperclips to the battery, the paperclips suspended the wire and completed the circuit, the wire acted as the moving motor and the magnet supplied the magnetic force. We put the paperclips on opposite sides of the battery and secured them with the rubber band, then we wrapped the wire in a circle with the ends sticking out on each side. Next, we rubbed off the coating on half of the side wires sticking out so each side has half coated and half not coated, this created an alternating current when the motor is spinning. Lastly, we put the wire on the paperclips and the magnet directly under the wire. The current carrying wire felt the magnetic force since it was perpendicular to the current. This force caused a torque that made the motor spin. This motor can be used in a blender, to make a fan, or even to turn the wheels on a car.
Another thing we learned about was electromagnetic induction. Electromagnetic induction is creating an electric current by changing the magnetic field through a loop of wires. The greater number of loops means a greater induced voltage, however, this also means it is harder to push a magnet through the loop of wires. This is because the induced voltage makes a current, which makes an electromagnet, which repels the magnet. Faraday's law states that the induced voltage in a coil of wire is proportional to the product of its number of loops, the cross-section between each loop, and the rate at which the magnetic field changes within those loops. Electromagnetic induction explains many things like how stoplights work. In the road there is a loop of wire. When your car, which is magnetic, drives over the loop it changes the magnetic field in the loop. This change induces a current that is a signal for the light to stop or go.
After electromagnetic induction we learned about generators. A generator is seen as more practical that a motor because you move the wire instead of the magnet and you input mechanical energy to get out electrical energy. Alternating current is necessary in a generator because the alternating current changes the magnetic field constantly, which induces the current of electricity. The greatest rate of change of magnetic field lines is when the number of enclosed field lines goes through zero. This is a podcast I did with Anna B. and Anna R. to explain both electromagnetic induction and generators!

Lastly we learned about Transformers and energy transfer from the power company to your home. A transformer has two loops of wire: the primary and the secondary. The amount of power is the same in the primary and the secondary coils, but the voltage and current can be different. There can be a high voltage and low current in, but a high current and low voltage out. A transformer uses alternating current so that the magnetic fields change in the primary coil to induce a current in the secondary coil. This changes the magnetic field of the secondary at he same rate. If the secondary has more loops than the primary, it will produce more voltage than the primary and this is called a step up transformer. If it has less loops then it will produce less voltage and is called a step down transformer. Some import an equations we used were that Power=Current xVoltage (P=IxV) and The primary number of loops over the primary voltage is equal to the secondary number of loops over the secondary voltage(Primary#loops/PrimaryV=Secondary#loops/SecondaryV). The power lines use transformers to decrease the amount of current as to save energy so that it is not lost as heat and decreases the amount of voltage throughout power lines so that our houses get the appropriate amount of voltage.

I found it most difficult to understand why alternating current was better than direct current and how it effected motors, generators, and transformers. As soon as we began talking about transformers and the changing magnetic field inducing current I finally understood. I really enjoyed making the motors, it definitely was not as difficult as the mousetrap car two units ago. In this unit I wish I had payed more attention to generators in class, but making the podcast really helped be understand them better. I really improved on the details of my homework, especially with the review sheet.

Motor Blog

In class I created a motor out of copper wire, two paperclips, a battery, a magnet, and a rubber band. The copper wire was made into an oval shape with two wires sticking out each side and carried the current from the battery, the two paperclips completed the circuits and held up the copper wire over the magnet, the battery was the energy source, the magnet provided the magnetic field which made the motor move, and he rubber band held the paperclips to the battery.
In order for current to get through the copper wire, you had to scrape off some of the plastic coating that covers the wire, but you would only scrape off the coating on one side of the wire because otherwise the motor would not spin in a circular motion, it would spin only spin in half turns.
In the motor the current is moving in one direction through the copper wire. The magnetic field acts as a perpendicular force against the copper wire causing torque.  If the force were not perpendicular, the wire would not move, however there would still be a force on the wire.
Here is a video of me with my motor working!
Margaret Anne's Motor
This motor could be used to make a fan, make car wheels, or even blades turn in a blender!

Magnetism

In this video Bill Nye explains how magnets work and why it is so. He uses the example of the earth as a giant magnet and explains what happens when you cut a magnet in half. A magnet has two poles, a north and a south. When a magnet it cut in half there is still a north and south pole on each half of the magnet. Like poles repel and unlike poles attract. When looking at electromagnetic fields, the field lines align when the south pole of a magnet across from a north pole of a magnet. Magnets are made of cobalt, nickel, and iron. Since the earth's core consists of this, the earth is a giant magnet.

Unit Blog

In this unit our class focused on many different aspects of electricity. I had most trouble understanding how electrons are not supplied to make a current, but do cause a current to flow. I really improved on my teamwork skills when dealing with a disagreement, but in this unit I wish I could have worked on my teams podcast more and been a better help.
First we learned about charges, charge transfer, and polarization. The two charges are positive and negative, a positively charged particle is a  proton and a negatively charged particle is an electron. Opposite charges attract and similar charges repel, so protons and electrons attract. You can create a charge in an object three different ways; friction, contact, and induction. When using friction you rub objects together to give it a charge. If you take off a sweater the friction against the sweater and your hair causes the electrons from your hair to move to your sweater. This causes your hair to be positively charged and stand up from the protons repelling each other. Unlike friction, induction does not require any contact. For example, if you have a neutral object and you put a negatively charged rod near one side of the object it will attract the protons and repel the electrons. Once the electrons are on the other side you give them a pathway to the ground, taking away the electrons and leaving the object positively charged.
Polarization is when you separate the charges on an object so that they are on opposite sides. In the video on polarization we watched, we learned that just because something is polar doesn't mean it is charged. Also, objects can either be conductors or insulators. A conductor  allows charges to move through it while an insulator does not. An example of this is saran wrap on a metal bowl, since it is a conductor the saran wrap wont stick to it, but if it were made of glass it would stick. In order for the saran wrap to stick there has to be a force. According to Coulomb's law the force and the distance between the opposite particles are inversely proportional (F=Kq1q2/d^2).
Electric fields are what surround these particles. They are the area around a particle that influence (push or pull) another charge. So, like in Coulomb's law if the opposite charge is closer in the field the stronger the force between the particles. Since everything has particles and charges are flying all around us, you would think that electronics would be effected by this. On the contrary, they are provided wit electric shielding. Since computers have very specific and delicate circuit boards that could be destroyed by charges, the are protected by metal casings. since the outside of an electronic is metal, the charges are moved strait from the electronic to the ground instead of into the circuits.
The next important thing we learned about was electric potential energy and electric potential. Electric potential energy is the potential energy of charges, for example, by pushing like charges together you increase the electric potential energy. The electric potential is the voltage and can be found by the equation voltage=Electric potential energy / charge (V=PE/q). Capacitors in hospitals use electric potential energy to create a large voltage so as to revive patients whose hearts stop working. Another example is the flash on a camera. Here is a podcast to help explain: http://www.youtube.com/watch?v=k7FemQMMJjE&feature=youtu.be
The most important thing we learned about, and most difficult, was current. Current is the flow of particles through a wire to create electricity. Current is caused by the difference in voltage in a circuit. The current flows from high to low so if the voltage on one side of a battery is 20V but the other side is 0V and they are connected by a wire, then the current would run from the 20 V side to the 0V side. However resistance could change the amount of current flow in a circuit. In order to increase the resistance and decrease the current you would either make the wire thinner, longer, hotter, or change the metal to a less conductive one. In order to decrease the resistance and increase the current you would  have to make the wire thicker, colder, shorter, or make the wire a more conductive metal. There are two different types of current, Direct and Alternating. Direct current is when a current continues to move forward while alternating current moves back and forth. Electrons are relatively slow and many people believe that power sources add electrons to make current flow since electrons are what make current flow, but these sources of power supply two different voltages as to make the high voltage move to the low voltage and create a current.  This is an example of a direct current as well and is what is the popular type of current to use.
Next, we learned about Ohm's law and power. Power=Current x voltage (P=IV) and Ohm's Law states that Current=Voltage/Resistance (I-V/R). This means that the current and resistance in inversly proportional. Power measures the amount of watts used my an object. For example, a LED light could use a60 watts, but a CFL only uses 13 watts. The less watts used the less current used and more electricity and money saved!
Last but not least we talked about series and parallel circuits. Series circuits are like adding stoplights whenever there is a new appliance to the circuit, they all effect each other and the current decreases with every new appliance. Unlike series, when adding appliances to parallel circuits it is like adding lanes to a highway. This means that the current increases when more appliances are added they are not effected by each other making it popular in house holds and cars, however, it can be dangerous. This is why there are fuses in homes. If too many appliances are plugged into one home the current could get so great that the wires over heat and cause an electric fire. The fuse act as a current cutter and shuts off the current by melting and causing a hole in the circuit. This stop the flow off current, the over use of appliances and heat from the wires.

Parallel Circuit Photo

 In this photo the lights from time square are connected by a parallel circuit, this way if one of the lighted billboards goes out the others will stay on. When the billboards are turned on a circuit is completed and current runs through the wires delivering electricity to the boards. This current causes the lights to turn on. Each light is connected by a parallel circuit so it doesn't effect the other lights if it stops working.