MAGNETISM
In this section, we learned about magnetism. This includes many interesting aspects for example what causes the northern lights, how credit card machines work, and many other topics.
Basics of Magnets.
Moving charges are the source of all magnetism. All magnets have a north and south pole, and the field lines run north to south inside, and outside, south to north. If you cut a magnet in half, it too will form a north and south pole. The earth also has a geographical north and south pole along with a magnetic field with a north and south pole. Domains are clusters of electrons moving in different directions. When domains are aligned, they form north and south poles. Like poles of a magnet repel, and opposite poles attract.
Compasses
The compass is a little magnet that can spin freely. The north end of the magnet attracts to the south end of the earth, while the south end of the magnet, attracts to the north end of the earth. This attraction causes the needle to align with the earth's magnetic fields. The north pole of the compass points to the correct geographic north because the earth's geographical poles differ from the earths magnetic poles.
How Can a paper clip become a magnet?
Originally, the paper clip is not magnetized. The domains within the paperclip are all moving in random directions. However, when a magnet is held up to the paper clip, the domains align, forming north and south poles. These north and south poles are attracted to other north and south poles, thus becoming a magnet.
Cosmic Rays
Cosmic rays enter the earth through the poles rather than the equator. This is because the force felt through the magnetic field of the earth, causes the rays to spiral around the equator into the poles. The poles run parallel to the rays, where as the equator runs perpendicular. The northern lights are caused by these cosmic rays entering.
Electromagnetic Induction
Out of everything that we have studied in this unit, I think that I struggle most with electromagnetic induction. Induction being a concept I had to wrestle a lot with last unit, it was difficult to see it again in an even more complex way. Electromagnetic induction is a way to increase voltage by changing the magnetic field in loops of wire. The change between a magnetic field and loops of wire, is what induces voltage. The more loops in a magnetic field, the more voltage, subsequently, the more resistance. When the magnet is inserted through or around the loops, there is a change in the magnetic field of the loops. The induced voltage also makes a current. The change in magnetic field also induces the current. The amount of current produced in electromagnetic induction depends on induced voltage, the resistance of the coil and the circuit, and the change in current in a nearby loop.
ApplicationIn the pavement, there is a loop of wire. When the car, which is magnetic, moves over the wire, it changes the magnetic field of the loop. This change in the magnetic field induces voltage, which causes a current. This current is a signal to the stoplight to change. Metal detectors and credit card machines undergo a similar process.
Generators
If you continuously change the magnetic field, that is how a generator works. Through electromagnetic induction, generators turn mechanical energy into electrical energy. (Mechanical energy is a magnet that moves, whereas electrical energy is current in a wire.
Generators use resources such as wind or water to turn loops of wire inside of a magnet. It relies on the change in the magnetic field rather than the force of the magnetic field. This change in the magnetic field induces voltage which causes current, which is the current we tend to use in our households
Motors
Motors are similar to generators, but Motors transform electrical energy into mechanical energy. Moving charged particles feel a force when moving perpendicular to a magnetic field. The force felt by the wire causes a torque. Motors work from the force of the magnetic field. Motors can be used for things like cars. Basically, a current runs through a coil, which feels a force because it is within a magnetic field (moving charges feel a force in a magnetic field). This causes the coil to spin, producing usable mechanical energy.
Transformers
A transformer is a device used for increasing or decreasing voltage or transferring electric power from one coil of wire to another through electromagnetic induction. A transformer is made up of two coils of wire. One wire is a primary coil, and the other is a secondary. The primary is is directly connected to the power source. Therefore, the primary is the input, the secondary is the output. Whenever the primary switch is open or closed, voltage is induced into the secondary current. AC current runs through the primary, which causes a change in magnetic field. DC cannot be used, because the current it produces only goes in one direction. The more turns in the wire, the more voltage is produced. If the secondary has more turns the primary it will produce more voltage than the primary and the voltage will said to be stepped up. If the secondary has less turns than the primary it will produce less voltage than the primary and the voltage will said to be stepped down.
FORMULAS
power in = power out
primary power/primary turns=secondary power/secondary turns
power=voltage x current
IV=IV
Vi=vI
ENERGY ALWAYS REMAINS CONSTANT
The area that I struggled most in, was electromagnetic induction. As I mentioned before, I had trouble with the concept last unit, and as it occurred in this unit also, it became even more complicated. I overcame this by looking at different people's blogs and talking to Mr. Rue for extra help. Additionally, I had issues with transformers, but I got over this by also looking at blogs and seeking extra help.
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