Unit 8 Reflection

In unit 8 of Physics, we studied magnetism and how it relates to electricity.  The concepts in this chapter were a  little hard to grasp, so I had to study alot outside of regular homework assignments.

The first topic we discussed was magnetic poles.  Every magnet has north and south poles.  Opposite poles attract, and same poles repel.  If a magnet were to be broken into two, there would be two equally strong magnets with their own poles.

Magnetism is produced by the motion of spinning charges called domains.  If the domains are all spinning in the same direction, or flowing in the same direction, they create a magnetic field.  Here is an image showing everything discussed so far:

As you can see, the flow of charges is from the south pole to the north pole.  The blue circle in the middle could in fact be Earth.  Earth is a magnet!  We have a North pole and a South pole.  More importantly, Earth's magnetic field protects us from harmful cosmic rays at most areas of the planet.  The rays cannot penetrate the magnetic field at the sides because they are going perpendicular to the magnetic field.  However, the rays can enter through the north or south pole, because they are moving parallel to the magnetic field.  This causes the popular "Northern Lights".

Another thing we talked about were motors.  Motors are simple apparatuses.  They are made up of an energy source, a magnet, and an armature of current carrying copper wire.  The energy source supplies energy to flow through the system, while the magnet creates a magnetic field.  When you turn it on, the armature feels a torque from the magnet and turns constantly in one way.  We made motors like this in class using a batter as our energy source.  The most important part was shaving the wire.  We could only shave on the bottom of the wire or else it would be pulled in different directions, and not flow steadily.  Here is a video of my motor at work:

Our next order of business was Electromagnetic Induction.  This was a tricky concept to understand.  The long and short of it is, when a magnet passes by a loop of wire, it induces a voltage, changing the current.  This is one of the most important aspects of physics, and it has been used to build appliances and machines all over the world throughout time.

In class, we looked very carefully at generators.  Generators use rotating coils and stationary magnets to turn mechanical energy into electric current.  A generator is essentially the opposite of a motor, in that a motor turns electric energy into mechanical energy and a generator turns mechanical energy into electrical energy.  This makes generators perfect for situations when there is a power surge.

Possibly the most important item we talked about was the Transformer.  A transformer has the ability to either step down or step up the value of voltage flowing through it.  It is made up of two coils of wire, one with more turns than the other.  When one magnetic field changes, it changes the other magnetic field, inducing a voltage.  It looks like this:

The purpose of a transformer is usually to keep objects plugged into the wall from burning up from the 120 Volts that come out.  Have you ever seen this little box on your laptop charger?

Yes, that is a transformer.  Since your computer can only handle about 10 volts, you need to step down the energy.  That is what this little box does.  This box gets very hot when it is in use because of the great value of voltage flowing through it.  It is important to note that transformers must use Alternating Current, so that the particles can change directions, in turn change the magnetic field about the primary.  If you must use DC, you have to turn the object on and off repeatedly to make the transformer work.

Overall, this chapter required a lot of memorization of basic concepts.  However, after I did memorize that stuff, it wasn't hard to synthesize it all into real world problems.  I really liked building the motor.  It helped me really visualize what we were talking about.