Last semester in our science class we learned about cells, measurements and genetics. This month, however we are studying electricity and magnetism, we have done many fun activities to be able to understand both these subjects. We started out with electricity and for that we build a simple electric motor, for magnetism we build an electromagnet using a simple nail, short amount of wire, two paper clips and a battery. But that was not all! We were then divided into groups of three and were each given a different topic of revision. These topics were covered in seven grade and we used this time to review the terms and learning goals.
Simple Electric Motor: The electric motor project was given to us as a starter to our new subject. Most of us did not know anything about it or had any idea on how to build it, but we used our sources and were capable to build the motors. In my case I watched videos and read about them on the Internet. Building the motor was very challenging, but it was easier to comprehend how it worked: The electric charge caused by the battery flows through the paper clips and on to the wire, but this is not all since this is not what causes the circle made of wire to spin. The magnet under the wire creates a magnetic field causing the wire to spin. Here is the picture of a simple electric motor that looks like mine:
Building an Electromagnet: We were then put into groups of three and build an electromagnet; this is a special type of magnet, since it can be turned on and off and it is usually used to transport something heavy, for example the cars in a car junk. This is how it works: The wire is rapped around the nail and connected to the battery. As the ends of the wire touch negative and positive on the battery, the metal part of the nail becomes a magnet that attracts the paper clips. As soon as you disconnect both ends of the wire from the battery the paper clip droops from the nail.
Goals:
1) How do electric charges interact?
The first revision goal was to answer the question: How do electric charges interact. Just as magnets, electric charges have negative and positive and they interact in just the same way. Positives repel positives, negative repel negative and positive and negative attract. All of the charge objects have an electric field around them, of course we cannot see them but they are very important on the interaction of charged objects. The closer the objects get, the stronger the electric field becomes.
2) How are charges transferred between materials?
There are three ways through which charges can be transferred. These are induction, conduction and friction.
In Friction two objects rubbing against each other transfer the charges. The object that loses the electrons becomes positive and the one that receives it becomes negative. An example of friction in real life is when you rub your sock against the carpet; your sock will have more negative charges than the carpet.
Conduction is when charges are transferred from one object to another by touching. In conduction the object with the biggest amount of positive charges will be the receiver of the negative charges of the other object.
Last but not least there is Induction, induction is the transferring of a certain charge to another part of the object because of the electric field around the second object. In induction the contact between the objects is not needed or seen.
3) How is an electric current produced?
“An electric current is the continuous flow of charges through a material” (pg. 45) Voltage is the one responsible for the production of electric currents, but the electric circuits are also very important since the charges flow continuously through these circuits consequently causing and creating an electric current.
4) I can compare conductors with insulator
Conductors: Materials that are conductors transfer energy faster; this is caused because the electrons in a conductor are able to move freely. Silver, aluminum and copper are examples of conductors. A wire is usually made of a conductor, since it allows charges to flow through easier and faster.
Insulators: Materials that are insulators decrease or stop the flow of charges; this is because the electrons in an insulator are bound together. Rubber, sand and wood are good examples of insulators. When there is a rubber protection around a copper wire, it is there to stop the current from the conductor to give you a shock.
5) How does resistance affect current?
For the current to work it depends not only on the voltage, but also on the resistance. The resistance is the difficulty that the charges have to flow through.
There are four factors affect resistance:
The first factor that affects resistance is the material of which the resister is made. If the resisters in a circuit are made of insulators it is efficient, since the insulator makes it harder for the charges to flow.
The second characteristic is the length of the wire, the longer the wire, the stronger the resistance.
The width of the wire also affects the resistance. In this case if the wire is wide the resistance will decrease, so if you want a good resistance the best one to use would be a thin wire.
The last feature of resistance is heat. If the wire is hot, the resistance is high and if the temperature decreases so does the resistance.
6) Use ohm law to calculate resistance, voltage or current
Ohm wanted to test the relationship between resistance, voltage and current. For this he build a circuit with a voltage between two different points of a conductor, he then measured how resistant the conductor was and finally calculated the current between the two points. With his results he found out that: resistance = Voltage/ Current.
7) How do you build series and parallel circuits?
There are two different types of circuits; there is the series circuit and the parallel one.
Series Circuit: The series circuit has only one path trough which current can be taken. This has disadvantages, since if one of the resisters or light bulbs breaks down the other ones will also stop working, since the current needs to get through one light bulb to get to the next one for the charge to keep flowing.
Parallel Circuit: The parallel circuit has different ways on which the charges can flow through. Each of these paths has their own resister or light bulb, so if one of them breaks down or simply stops working, the charges would change their way and flow through the other resister, causing it to keep working and not break the current. In parallel circuits the light bulb are usually brighter than in a series circuit.
Parallel:  |
| http://www.google.com.br/imgres?q=parallel+circuit+ diagram&num=10&hl=pt-BR&gbv=2&biw=1073&bih=70 4&tbm=isch&tbnid=ZFrk4TxZhm87jM:&imgrefurl=http://kimberleyparkss .eq.edu.au/home/jmann30/science.html&docid=bQuauwnd1jIpXM&imgurl=http://kimberl eyparkss.eq.edu.au/home/jmann30/Website%252520pictures/parallel1.gif&w=423&h=356&ei =96NCT8bdJ4XY2QXS7JSDCA&zoom=1&iact=rc&dur=282&s ig=109156476607484567813&sqi=2&page=1&tbnh=161&tbnw=191&start=0&ndsp=12&ved=0CFkQrQMwBg&tx=127&ty=1 14 8) Explain the relationship between power, voltage and current Power is the transformation of energy from one form to another. Power is used al over us, in our hair driers, televisions, alarm clocks, stove, microwave, refrigerator, computer, clock radio and many others. Watts (W) is the unit used to measure power. For example, a socket can be 110W or 220W, so you have to be careful as to which devices can be plugged in each of the sockets. The formula for calculating power is: Power= Voltage X Current. Reflection: When we first got the motor project, I will confess I was a little bit scared, since even though it looked easy to build it was not. I had many problems with my motor. I changed the material many times: the wires, the battery and the paper clips, but not even that worked. I asked many people to help me but it was still challenging. I did manage to understand what was wrong with my motor and it finally did move. The electromagnet was easier to build, but harder to understand how it worked, I still have doubts but the basics are clear, especially because of the examples given in class. The revision goals were also very hard for me to understand. The concepts and basics of each one are easy for me to explain, but when they go more into depth I am completely lost. I am studying and created many outlines, which helped me loads as to understand the basics of all eight goals. In general, these first two weeks of Science Class were full of projects and revisions that helped me remember and comprehend many energy related subjects, but I do believe I could go further and study even harder to have no problems with this wonderful subject. |
