The Past Two Weeks of Class!

When we started classes we were asked to build a simple electric motor. It was a challenge for us because we had barely studied electricity, and we had to find the motor we wanted to build, the necessary informations for building it, and buy all the materials. At first I built the "plastic cup motor" that you can see in the video in the link at right;  http://www.youtube.com/watch?v=ziWUmIUcR2k. This video is a very good source of information, because it is detailed, and clear; however it is not easy to built the motor as it looks in the video. I only could find a wire that was too heavy, so it would not spin when arranged as a coil, also the alligator cable clips wouldn't connect to the battery as it is shown in the video. Another problem that I could identify in the video is that it does not says how potent your magnets should be, because if you use weak magnets, as I did, the coil will not spin either. As a consequence of all those factors my plastic cup simple electric motor didn't work.

After building our motors we were asked to bring them to class so that we could show to our colleges and exchange ideas. My college showed me a simpler motor that I could easily built, and would not need to buy additional materials. So I built the motor, and was relieved that it worked. You can see how to built this simple motor in the pictures bellow, they are not accurate, but with them you can have an idea of how this motor works.

You can see all the materials that are need to built this motor.

You can see how to arrange the materials so that the motor can work.

You can see what happens when the motor is working.

After managing to build a simple electric motor we were split into groups, and each group was given a topic so that we could understand why our motor worked or did not. My group was given the topic; transferring chargers. We did a poster with drawings explaining our topic, and after presented briefly to the class. We explained that there are three ways in which chargers can be transferred; charging by friction, charging by conduction, and charging by induction. Charging by friction is the transfer of electrons from one uncharged object to another by rubbing. For example if you are walking in a carpet with your socks on and you rub them in the carpet, electrons will move from the carpet to your socks causing an overall negative charge on them. Charging by conduction is the transfer of electrons from a charged object to another object by direct contact. For instance when your socks that are now negatively charged touch your skin the electrons present in it will be distributed throughout your body. Charging by induction is the movement of electrons to one part of an object that is caused by a electric field of a second object. For example when you touch a doorknob after walking in a carpet with your socks on your fingertip produces an electric field that repels the electrons in the surface of the doorknob, and will move away from your finger. This movement will produce an induced positive charge on the doorknob.

After all groups presented we were expected to achieve eight learning goals that were stated like this;

1. I can explain how electrical 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 compare resistance, current or voltage.

7. I can built series and parallel circuits and describe them.

8. I can explain the relationship between power, voltage and current.
I still can't understand why my simple electric motor worked. I know that a circuit was created between the battery and nail, and that the voltage in the battery caused a current. The wire was made of copper which is a conductor so that charges could flow. The charges in the wire went to the nail, that was also a conductor because it was made of metal, and at last they went to the magnet. I don't know about the magnet's role, but I can deduce that it was the responsible for making the nail spin. I am not sure why the nail spun after that, I think that it has something to do with the chargers being in contact with the magnet, and their electric field interacting with the magnet's magnetic field.
Did I achieve the eight learning goals?
1. I can easily explain how chargers interact. Positive chargers repel each other, negative chargers also repel each other, and positive and negative chargers attract each other. Summarizing; chargers that are the same repel each other, while chargers that are different attract each other.

2. I can give examples of how charges can be transferred between materials and explain them as I just did in the third paragraph where I explain the topic that my group was given.
3. An electric current is the continuos flow of charges through a material, but it requires an electric circuit to be be produced. An electric circuit is a complete, unbroken path through which chargers can flow. Imagine you have a circular race track, and cars are moving continuously through it. They make many turns, and keep moving through the race track. The move of cars is equivalent to current. If the race track was broken the cars would not be able to move, it provides that the cars are able to move continuously. The race track is equivalent to a circuit.
4. A conductor is a material through which chargers can flow easily. Atoms contain electrons that are bound loosely in a conductor. Conductors have less resistance, consequently charges will always choose the path of a conductor, because they always choose the path of least resistance. Because of that conductors are often used to carry electric charges. An insulator is material through which charges cannot flow easily. The electrons are bound tightly to their atoms and do not move easily in an insulator. Insulators have more resistance, so chargers will never choose the path of a insulator, because they always choose the path of least resistance. Because of that insulators are often used to stop the flow of charges.

5. Current depends on voltage and resistance. Voltage is like a push for the flow of electrons start. It requires a source of energy, a battery, to maintain itself. Resistance is the measure of how difficult it is for charges flow through a material. As resistance increases in a circuit, the current's speed decreases. The greater the resistance, the less current there is for a given voltage.
6. Ohm's law says that the resistance is equal to the voltage divided by the current.

7. If all the parts of an electric circuit are connected one after another along one path, the circuit is called a series circuit. In a series circuit, there is only one path for the current to take. If a light bulb burns out in a series circuit the circuit will be broke and there is no other path for the current to take. So if one light bulb burns out, the others won't have their lights going on as well. The light bulbs in a series circuit becomes dimmer as more bulbs are added, because the resistance increases and the current decreases as there is just one path to take. In a parallel circuit, the different parts of the circuit are on separate branches. In a parallel circuit, there are several paths for current to take. If a light bulb burns out in a parallel circuit the circuit will not be broken, because charges will still be able to move through the other branches. One light burning out does not affect the other lights, as there are more paths in which current can take. If you add a light bulb in a parallel circuit the brightness of the other lights in the other branches will not be affected, but the battery will run out faster.

8. The rate at which energy is transformed from one form to another is known as power. The unit of power is the watt (W). You can calculate power by multiplying voltage by current.

Power= Voltage x Current

P= VI

Using Google Docs we had to create a multiple choice quiz of 10 questions applying all the concept of those topics. The quiz could not include formulas and definitions, and as you can see I posted on my blog so that everyone can have a chance to do it. Some of the topics that I couldn't quite understand at first were 7 the one about series and parallel circuits and 6 the one about Ohm's law. If you are having trouble to understand series and parallel circuits you can click on this link;http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc. If you click on the link, and in the website click "Run Now!" you will be able to built parallel and series circuits and see how they work. It helped me a lot, and now I can finally understand them. To understand Ohm's law I just needed to review carefully my book, and after some minutes I could get it.

My goals for this semester are; putting my best effort, and managing my time well. Managing my time well is my most important goal, because last Semester I didn't do it so, and eded with late works, and little time to study. I will a try to be more organized in this semester, and hope that in consequence I will achieve better grades, and will end 9th grade without doubts.