The first thing that we talked about was magnets and magnetism. The term magnetism comes from magnesia, a place in greece where lodestones had intriguing properties of attracting pieces of iron. The source of all magnetism is moving charges. This is very important to remember. Adjacent atoms cause clusters to line up with one another. These are called domains. Domains of ordinary iron are not aligned, the are random. They need to be magnetized. Before magnetism, there is no net direction. When a magnet comes in contact with the ordinary iron, the domains will align in the same direction as the magnetic field of the magnet. This ordinary piece of iron will not have a north and south pole because it's domains are aligned.
In a magnet there is a north and south pole. The magnetic field of a magnet runs down to the north pole, up, around, and down through the south pole. If you have a south pole of one magnet and the south pole of another magnet, they will repel each other. This is because they are both pulling in so away from the outside. Same with the north pole. They will repel because they are both pushing out, therefore they will repel each other. Also, like poles attract.
We had a big question of how a paperclip sticks to a magnet, lets figure it out. The domains in the paper clip are spontaneous. The magnet has a magnetic field. When the magnet comes in range of the clip, the domains of the paperclip align and match the magnetic field of the magnet. The paper clip now has a north and south pole because it has aligned domains. The north pole of the paperclip is attracted to the south pole of the magnet. Thus, they stick together.
We also learned about electromagnetic induction. Electromagnetic induction occurs when you have a loop of wire with a complete current. Insert a magnet through or around the loop of wire and that changes the magnetic field of the loop of wire. This change in magnetic field induces a current. We can do things with this current because it acts as a signal. This will help to understand how credit cards work. In the credit card machine, there is a loop of wire. When the card, which has a strip with a series of magnets, moves through the wire, it changes the magnetic field and induces a current in the wire. This current acts as a signal and tells the computer what your credit card number is.
We also talked a little about motors. At this time we learned the gang sign rule. Your index finger represents current, middle finger represents magnetic field, and your thumb is the direction of the force. In order for a motor to work it must have a current carrying wire and a magnet. We made motors in class using a battery, paperclips, wires, a magnet, and a rubber band. The battery supplied the energy. The paperclips carried the current and completed the circuit. The wire, which we coiled, became the current carrying wire. The magnet provided the magnetic field. This made a motor because the loop of wire was located above the battery. The current carrying wire felt a force from the magnetic field of the magnet and this forced it to turn. Remember, there needs to be torque for an object to spin, without torque the wire wouldn't have spun. Also remember that the flow of electrons must be parallel to the magnetic field to feel a force. This is electrical energy being turned into mechanical energy.
The opposite would be a generator where you input mechanical energy and get out electrical energy. Also in a generator the loop of wire does not require a current and it is surrounded by a magnet.
Transformers was the last thing that we learned about. Transformers can basically step-up or step-down voltage. They have a primary and secondary coil. In each coil the power is the same. In the primary and secondary, the more loops of wire you have the more voltage that is induced. Transformers only use AC current because it will cause the magnetic field to change. Without a change in magnetic field, there will be no voltage induced.
This unit has been pretty fun. We had a hands on experiment that really helped me to understand the topics of motors and some of the rules of magnetism. Also there happened to be math in this section which made understanding transformers a lot easier.
My efforts to classwork and homework this unit were stelar. I am pretty sure I handed everything in and always completed my classwork. I felt way more focused this unit and also there was a level of interest that I had that I felt pushed me forward to better my understanding of the material. I hope to finish out the year with this attitude towards physics.
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