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.