miércoles, 18 de abril de 2012

Learning Goals!

On my last post, I introduced and explained the first 8 goals from the total of 21 goals from my worksheet which I need to answer in order to demonstrate my understanding of EM forces.  Of course, to learn I need to use sources which provide me with information. However, my teacher found a more productive way of learning, by using simulations and images. Anyways, the rest of the goals are answered below, starting from the ninth one.

EM9. I can describe the properties and interactions of magnets.
Magnets have three properties in common; they attract iron and materials that contain iron, they attract and repel other magnets, and one part of the magnet will always point north when allowed to swing freely.
Magnets interact in two different ways. They can either attract or repel each other. When unlike poles are brought together, they will attract each other. On the other hand, when like poles are brought close to each other, they will repel.
http://27gen.blogspot.com.br/2010/10/so-you-have-magnetic-personality.html
EM10. I can describe how the magnetic domains are arranged in a magnetic/non-magnetic material.
The magnetic fields of the atoms in certain materials are arranged differently depending on whether they are magnetic or non-magnetic materials. Magnetic materials have all or most of  its magnetic domains aligned in one direction. The magnetic domains of non-magnetic materials is the opposite, the domains aren’t aligned or point to random directions.


EM11. I can explain the connection between electricity and magnetism (electromagnetism).

According to my science textbook, electromagnetism is the relationship between electricity and magnetism. An electric current produces a magnetic field. Electromagnetism cannot be seen yet, we can observe its effects by using a compass and an electric field. Usually, a compass’ needle aligns itself with Earth’s magnetic field. However, it will point in a different direction when a current is present. In other words, the needle will align with the magnetic field produced by the current.





EM12. I can outline the difference between DC/AC current and its uses
In an induced current, charges may flow in one direction or alternate direction. A current which consists in charges flowing through one direction is a direct current or DC. An alternating current or AC consists in charges which continuously move back and forth in a circuit. Whether an induced current is AC or DC depends on the direction in which the wire or magnet moves.
Direct current are used for simple circuits. On the other hand, an alternating current can be used to send electrical energy over great distances and for our everyday devices due to its ease of raising and lowering its voltage in the circuit.
EM13. I can explain why the Earth behaves like a magnet and the consequences of it.
Earth is considered to behave like a magnet since it has a magnetic field and magnetic poles.  Both of the magnetic poles form a magnetic field, to which compasses align with. Also, by having a magnetic field, Earth can make magnets from ferromagnetic materials. By leaving an iron bar lying for years, the Earth’s magnetic field can attract its domains so strongly and make them line up in the same direction.

EM14. I can explain the importance of grounding wires and using fuses/circuit breakers.
All of them are safety devices which prevent people from getting an electric shock. Grounding wires provide an alternate path for a current. This path provides a current's charges to flow from the circuit to the earth. One type of grounding wire is the third prong. A plug usually has two prongs which connect to the a house's circuit. Yet, have you ever wondered why some plugs have a third round prong? A third prong connects the appliance with the ground wire of a building. So, if a short circuit occurred, the charge would flow to the Earth, preventing you from having an electric shock.
Fuses are devices that have a thin strip of metal which will melt if there's too much current, to break the circuit and avoid fire. Hoever, when the fuse is used, it must be replaced in order to protect you. For this reason, circuit breakers are used to avoid replacing fuses. Circuit breakers also breaks a current when there's too much and compared to fuses, it is reusable.
Third Prong:

http://web.princeton.edu/sites/ehs/labsafetymanual/Image18.gif
Circuit Breaker:

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjzSiKsHhERvn08ifHInKS_aT-RNGGpMhQ98gdowVl0hRXpUPOCyA9RuLjm_FuZJ4akTfw5p4lGPCq-4vTbhFA5_YavYbfbAv6BkUBhVR9Wp7T_3NE-EpdNYTBwLfp8DnzDlVLE1twVheI/s400/circuit-breaker.png

EM15. I can explain how an electromagnet works and cite applications for them.
An electromagnet is a solenoid with a ferromagnetic core. Its magnetic field is produced by the current in the wire and the magnetized core. The electromagnet’s strength can be increased in several ways: by increasing the current in the solenoid, by adding more loops of wire to the solenoid, by winding the coils of the solenoid close together, or by using a stronger ferromagnetic material for the core. It really useful since you can make act as magnet whenever you want, it can be turned on and off at any time.


EM16. I can explain how a simple motor works (parts and function).
Electric motors are devices that use electrical energy to produce motion. In other words, it transforms chemical energy into mechanical energy. However, how does it work exactly? First of all, a battery is connected to the motor, which gives a push to the charges that are already present in the wire of the motor. The wire connects to the brushes which allow the current to go to the commutator, with which is connected. The commutator will then allow the current go to the armature. When the current is in the armature, its magnetic field will interact with the magnetic field of the permanent magnets which are next to each side of the armature. At this moment, the armature will act as a magnet, causing the the armature and the permanent magnet to repel each other. In other words, the armature will make a half turn. This will change the direction of the current since when the electrons reach the commutator, a new and faster impulse of electrons will push and make them follow their path. This process repeats various times to make the armature flip continuously, until the battery runs out.


EM17. I can describe how a generator and a transformer work.
Generators are devices that transform mechanical energy into electrical energy. There are two types of generator: AC and DC generators. In an AC generator, the armature is rotated in a magnetic field, inducing an electric current in the armature and causing the current in the wire to change directions. DC generators work like electric motors yet, you spin the motor to produce electrical energy.
Transformers are devices that increase or decrease voltage. There are two types of transformers,step-up and step-down transformers. Step-up transformers increase voltage and has its secondary coil with more loops than the primary coil.  On the other hand, step-down transformers decrease voltage and its primary coil has more loops than the secondary coil. 
Step down transformer:


Step up transformer: 


EM18. I can explain the importance of transformers to power grids.
Transformers are important in the transmission of electrical energy from generating plants, in order to be safe. First, we use step-up transformer to increase voltage, to efficiently transfer current over long distances. However, the voltage must be decreased, by a step-down transformer, for the current to be safely used in homes.


EM19. I can explain methods of power production and distribution.
There are numerous ways of power production and distribution. Some of them include: fossil fuels, nuclear energy, hydroelectric energy, biomass, solar energy, wind energy, and geothermal energy.

Fossil fuels are non-renewable energy source formed over millions for years from the remains of plants and animals. When burned, they release energy. They are transported to power plants, where they are burned to heat water. The steam from the water then increases in pressure, forcing the turbine to spin. The turbine is used to rotate a magnet encased in a generator at high speeds. As the magnet spins, electrons are produced, and they power the electricity grid.  

Nuclear energy is energy provided from an atomic nucleus through nuclear fission. The nuclear energy is converted to steam energy (heat generated by the nuclear fission is used to heat water). This energy is used to drive a turbine generator (mechanical energy) and produce energy.




Hydroelectric energy is the production of electrical power through the use of the gravitational force of falling or flowing water. It is generated by taking advantage of the difference in height of water behind and in front of a dam. This water has potential energy. The water is fed down huge pipes and into large turbines where the water spins the wheels of the turbines which in turn are attached to large electrical generators.


Biomass are plant materials, vegetation, or agricultural waste that are used as fuel or energy source. The materials are gathered in big trucks and then transported to a biomass plant. There, the wastes are fed into the furnaces where they are burned. The heat created is used to boil water and the energy from the steam that is created, is used to rotate turbines and generators.


Solar energy is the energy received by the earth from the sun. A system absorbs solar energy (like a photovoltaic system) and then converts or transforms it into a storable form of energy.

Wind energy is energy received from the movement of the wind across the earth. Wind power is produced by using a wind generator which converts the kinetic energy available in the wind to mechanical energy.


Geothermal energy is the energy derived from the heat in the interior of the earth. There are three different types of power plants used to generate electricity from geothermal energy depending on the temperature, depth, and quality of the water and steam of the area. In all cases, the condensed steam and remaining geothermal fluid is injected back into the ground to pick up more heat. In some locations, the natural supply of water producing steam from the hot underground magna deposits has been exhausted and processed waste water is injected to replenish the supply. Most geothermal fields have more fluid recharge than heat, so re-injection can cool the resource, unless it is carefully managed.


EM20. I can describe the differences of 110v/220v and main advantages and disadvantages of each.
A higher voltage, 220v, provides homes with a major amount of force to push an electric current. With a fast moving current, more electricity can go to homes of a city. On the other hand, 110v provides with a smaller amount of force to push an electric current yet it is more common. Also, if you were to receive an electric shock, with 110 volts would be less painful than with 220 volts.

EM21. I can describe the advantages and disadvantages of electrical energy.
Some advantages of electrical energy are that it is easy to move from one circuit to another, it’s safe, and it can be transmitted for long distances. Some disadvantages include that it contributes to global warming and isn’t permanent during storms.


viernes, 17 de febrero de 2012

Science Class During the Past Couple of Weeks

 During the past two weeks of school, I built an electric motor and reviewed the first eight electricity goals. An electric motor transforms electric energy into mechanical energy.  In order to build it, you will need the following materials: 

- An alkaline battery type D
- Tape
- Two paper clips (the larger the better)
- A rectangular magnet (such as those used in refrigerators) 
- A toilet paper tube (with a small diameter)
- Thick enameled copper wire
- Sandpaper
- Optional: glue, small block of wood for the base

Instructions:
1.      Roll the copper wire around the carton tube, 10 0r more times (in parallel coils), leaving at least 5cm from each unwound ends and PERFECTLY strait. Remove the tube since it is only used to build the coil. The wire can also be rolled around any other cylindrical objects. For example, the “D” type battery itself.

The ends must match. In other words, they must face each other since they are the shafts of our motor. You can either use a drop of glue between each turn or give two turns to the wire of the ends from the coil to prevent its distortion.

2.     Using the sandpaper, completely remove the enamel of the wire of one of the ends of the coil. Leave at least 1 cm without sanding, the part that is closest to the coil.

3.     Place the coil on a flat surface and sand the other end of the wire. Again, leave at least 1 cm without sanding, the part closest to the coil.

4.     Fasten the magnet to one side of the battery by using glue.

5.     Using the paper clips, leave two hooks on each end having between them an angle of 90 degrees. Flat pliers or with a fine tip can be very useful.

6.     Use the tape to fasten a paper clip to each end of the battery, placing the ends on the same side of the magnet.

7.      Hang the coil on the free ends of the clips. If the coil doesn’t spin, immediately you should slightly help it.


Explanation:

When we place the coil on the ends of the clips, we close the circuit so that a magnetic field is induced in each of the turns of the coil. The electric current is generated by the battery. Anyways, the electric field faces the magnet itself, originating the rotation of the coil.  The coil will stop spinning when the electric current stops to flow. In other words, when the battery runs out since the wire is only sanded by one side of one of the ends of the wire and a static equilibrium of the whole will never be achieved.  If both sides were sanded, equilibrium between the electric fields would be produced, generating no movement.
If the motor doesn't work, make sure that the clips are making contact with the poles of the battery, that their surfaces are well sanded, or change the lateral position of the magnet. These were some of the factors of why my motor didn't work. 


*I couldn't post any images of my motor since it didn't work and I undid it before my teacher told me to provide an image of it in my post.  



Reviewing Electricity Goals:

            Building the motor introduced me to a new topic: Electricity. Later on, we reviewed some concepts from 7th grade about the same topic. There were a total of eight goals we reviewed which are listed as follows:

1.      I can explain how electric charges interact
2.     I can give examples of how charges can be transferred between materials and explain them.
3.     I can explain how an electric current is produced
4.     I can compare conductors with insulators
5.     I can explain how resistance affects current
6.     I can use Ohm’s law to calculate resistance, current or voltage.
7.      I can build series and parallel circuits and describe its parts.
8.     I can explain the relationship between power, voltage and current.

There are three types of electric charges: protons (+), electrons (-), and neutrons (o).  The relationship between them is simple: opposites attract and likes repel.

Charges can be transferred from one object to another by three methods. One of them is charging by friction, the transfer of electrons from one uncharged object to another by rubbing. The second method is charging by conduction, the transfer of electrons from a charged object to another by direct contact. The third way is charging by induction, the movement of electrons from a part of an object to another which is caused by the electric field of a second object.

charging by friction

http://media.ehs.uen.org/html/PhysicsQ3/Charging_by_Friction_01/charging.jpg

charging by induction
http://media.ehs.uen.org/html/PhysicsQ3/Conduction_and_Induction_01/induction1.jpg
charging by conduction
http://media.ehs.uen.org/html/PhysicsQ3/Conduction_and_Induction_01/conduction.jpg

  












An electric current is the continuous flow of electrons. It is produced by the continuous flow of charges from one place to another.  In the following image of a car circuit, a simulation of what happens inside an current is present. The car circuit represents an electric current itself while the flowing charges are being represented by the cars. 
Furthermore, there are four factors that determine resistance: type of material the wire is made, temperature, diameter and length of the wire. The type of material the wire is made of refers to whether it is a conductor or an insulator. If the wire is an insulator, it will make it difficult for electrons to move through the current since it has tightly held electrons. In other words, it has more resistance. If the wire is a conductor, it will make it easier for electrons to flow through the current since it has loosely held electrons. It has less resistance. The second factor is temperature. As temperature increases, the resistance of the wire increases too. In contrast, as the temperature decreases, the resistance of the wire does as well. The third factor includes the length of the wire. A short wire has less resistance than a long wire. Lastly, the fourth factor that determines resistance is the diameter of the wire. A wide wire has less resistance than a narrow wire. 
http://www.woodentoys123.com/products/race-car-circuit-toy-1.jpg
Conductors and insulators are different groups of materials. Insulators are materials through which charges can’t flow easily. Conductors are the opposite, they are materials through which charges can flow easily and are used to carry charge, and they have less resistance. 
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDwd3i-xchUbhPD3coK289Tcbhyphenhyphen8bHxMn3Aqh-ufmQoPp4-Xz8Q8tskGow-3aYt0tjB0tP84-vNkUAXksfDTFkqhpyPiL6-rHVzigF_-L6x-W58HNUEjaJdAhKpavmFayX-VQ1s3L279I/s1600/IMG_1872.JPG

Resistance is the measure of how difficult it is for charges to flow through a material. When resistance increases, the current decreases. There are four factors that determine resistance: the type of material, length of the wire, diameter of the wire, and temperature.
Ohm’s law is used to calculate resistance, current or voltage. The equation is resistance equals voltage divided by current (R=V/C).  When resistance increase and current remains the same, voltage increases. On the other hand, when resistance decreases and voltage remains the same, current decreases.
http://www.hondaforeman.com/attachments/how/7309d1318956570-electrical-system-explained-how-500px-ohms-law-triangle.jpg

There are two types of circuits: parallel and series. A parallel circuit has several paths while a series circuit has only one. The different parts of a circuit are the energy source, resistors, and a switch. The energy source is what makes charges move around the circuit. A resistor resists the flow of an electric current. The switch is used to open and close the circuit.

Another essential formula in electricity is P=VI, which represents the relationship between power, voltage and current. P represents power, V represents voltage, and I represents current. Power is the rate where one type of energy is transformed into another. 
http://www.sengpielaudio.com/FormulaPower01.gif


Self-Reflection:
In my opinion, building an electric motor helped me visualize how it works more easily. It was a more didactic and entertaining way of learning instead of just reading the book. Same thing goes with the goals. By performing different types of activities to learn, it helps maintain the concepts in my mind without the need of memorizing it. 



lunes, 13 de febrero de 2012

Electricity Quiz!!

It´s quiz time! Please take the quiz at the bottom, it will only take a minute to complete. 
Good Luck!

viernes, 28 de octubre de 2011

Cells Summative Assessment

During the past weeks, I have been working on a cell summative assessment.  Its purpose was to give our science teacher a tool that could be used with the students. The project could be a comic book, storybook, newspaper, game, song, talk show, etc. I decided to write a song.

  My initial plan was to create a website, which didn´t work at all due to a few technical problems. I gave up with 6 days remaining!! I couldn´t decide which project was more suitable for me until the weekend was left. So, I thought writing a song wouldn´t take me much time. Though, I was wrong. Writing the lyrics took me a whole day. Still, I hadn´t finish the entire project. My teacher requested a video which explained my work. Yet, what would I explain if it was a simple song about cell division? Ms. took this into consideration and told me to record it!?! I almost passed out but I had no choice. Despite the fact of my voice, practicing the song helped me remember each step of the cell division process without studying!

At the end comes my self-evaluation. Since I only worked on my project during the last weekend, the quality of it isn´t the most favorable. At least, it became a more interacting and fun way of learning science. The lyrics are provided below so feel free to check it out.

Lyrics:
How do Cells Divide
Ohh
How do cells divide, over and over again
A message to the man ohhh
The sequence of events, preparing to divide
Into two new cells

Let’s Go!!
Yeah, you listening now
 At interphase the cell grows to its mature size
 The cell makes an exact copy of the DNA
 At the end it has two equal sets of DNA
 Preparation in cell division beginns ahaa
 Produces structures that will be used ahaaa
 The next event of the cell cycle is prophase
 Chromatin in the nucleus condenses to form chromosomes
 The pairs of centrioles, move to opposed sides
 Spindle fibers form, a bridge from the end- sides
 The nuclear envelope breaks down
 Then is metaphase, chromosomes line up in the center of the cell
 Each attaches to spindle fibers at its centromere
 Stop making this so hard for me, damn
 I used to be a kid that couldn´t solve this out
 That’s why you have to keep singing till you understand

Ohh
How do cells divide, over and over again
A message to the man ohhh
The sequence of events, preparing to divide
Into two new cells

Yeah, anaphase is next
Two chromatids split becoming two new chromosomes
The new chromosomes
Begin moving to the opposed ends of the cell
It stretches out as the opposite ends are pushed apart
At the end, each pole has a complete pile of chromosomes
 At telophase, chromosomes begin to stretch out and lose
 Mate, now my song would leave them amazed
Great, it feels like a hard time fading out
Since the day I thought of that cunning plan
But I´m missing something I try to remember
Which belong to this song, the final stage!
It’s Cytokinesis, where the cell splits in half
Each ending with alike sets of chromosomes
 Everyone’s a kid that couldn´t solve this out
 You just gotta keep singing till you understand


How do cells divide, over and over again
A message to the man ohhh
The sequence of events, preparing to divide
Into two new cells

Ohh (4x) Interphase
Ohh (4x) Prophase
Ohh (4x) Metaphase
Ohh (4x) Anaphase
Ohh (4x) Telophase
Ohh (4x) Cytokinesis

I know how cells divide, over and over again
A message to the man ohhh
The sequence of events, preparing to divide
Into two new cells