Build-it-Yourself Motor

Recently in physics class, we all undertook the task of assembling a simple motor.  An Electric Motor is defined as an object that utilizes both magnetic fields and current-carrying conductors to generate a force.  To assemble the motor, I needed the following objects:

• Battery- The purpose of the battery is to provide the electric energy for the rest of the system.
• Magnet- The purpose of the magnet is to create a magnetic field around the system which can interact with the current-carrying conductors.
• Copper Wire- The purpose of the copper wire is (when shaved properly*) to feel the magnetic force and move properly.
• Paperclips- The purpose of the paper clips is to suspend the copper wire above the battery and the magnet, and also to carry the current to the wire.
• Rubber Band- The purpose of the rubber band is simply to bind the paper clips to the battery.

Here is a picture of a make it yourself motor with a similar design to ours.  The only difference is that alligator clips were used to supply energy instead of our battery:

*Before the motor would work, the copper wire had to be scraped.  It was scraped on the bottom of both sides of the wire.  This made it easier for the wire to feel the torque of the magnet.  When the wire felt this force, the current flowed through the wire, and it turned.  It was very important for us to scrape the wire properly, because if we scraped it on the top and bottom, the wire would want to turn in different directions and it would not move straight constantly.

This simple concept can be used in large scale in cars, lawn mowers, fans, and blenders.  If you were to open up one of these appliances, you would see a huge coil of copper wire, and a magnet.  When applied to a larger scale, this design can be used to generate alot of mechanical power.

Here is a video of my motor at work!

Unit 7 Reflection (Not Finished)

This long unit covered all aspects of electricity in physics.  The first concept we looked at was that of electrostatics.  Electrostatics is the study of electric charge that is at rest, that is to say, there is no current.  We learned alot in particular about how things become charged.  There are a few ways in which something can become charged:

• Contact-Something can be charged by friction or touching when one object steals valence electrons from another.  This is common in clothes driers.  In the drier, since there is alot of friction, some clothes steal electrons from other clothes, making some clothes positively charged and others negatively charged.  Since opposite charges attract, the clothes will stick together when they come out of the drier.
• Induction-Objects can be charged by induction when they are close but not touching.  Here is how the process goes:

1. The objects touch, resulting in one uncharged conductor.
2. Negatively charged object is brought near one side of one object.
3. Since opposites attract, the charges are forced to repel and reorganize, at separate ends.
4. The objects are pulled apart, creating one negatively charged object and one positively charged object.

• Polarization-Objects can be charged through polarization when one side of an object has many positive particles, which attracts to an object with negative particles on one side.  This is commonly seen with balloons when they stick to walls.

Another important subject we studied is Coloumb's Law.  It reads:

F= k q1q2 / d^2

This law is a mirror image of the universal gravitational law.  Similarly, as distance decreases, the force of electric attraction between two objects increases.

We also talked about conductors and insulators.  Conductors are objects that allow electricity to flow very easily.  Metal is an example of a conductor.  Insulators are objects that do not allow electricity to flow easily.  One question we were constantly faced with was: Why does saran wrap stick easily to a ceramic bowl, but not a metal one?

The answer is: The saran wrap sticks to the ceramic bowl because its electrons are not allowed to flow through the bowl and out because the bowl is an insulator and the electrons are caught inside it.  With a metal bowl, electrons easily flow through the bowl and out, making both the saran wrap and the bowl uncharged.  Without charge, the two will not stick to each other.

We also discussed electric fields.  Electric fields seemed very simple because I already took chemistry, and we dealt with E- fields very often.  They can be defined as "auras" surrounding a charged object.  The arrows coming out of the inner circle are very important as they represent the magnitude and direction of the electric field.

The last item we studied in Chapter 22 was Electric Potential.  This is where we were introduced to voltage.  the equation for Electric Potential is:

Voltage = electric potential energy / charge

Electric potential lead us into the second half of this unit, in chapter 23 entitled "Electric Current"

The first item we discussed in this chapter was electric current.  Electric Current is the flow of electric charge through some sort of line or wire.  Electric resistance counteracts electric current in that it is the property of material to resist the flow of electric current.  There are few different ways you can change the resistance on an object:

• Thickness- A thinner filament will increase the resistance, decreasing the electric current.
• Heat- As heat increases, so will the resistance, causing the electric current to decrease.

Once we knew all about current, voltage, and resistance, we learned about Ohm's Law.  Ohm's law is written as:

Current = Voltage / Resistance 

This equation shows us that resistance is inversely proportional to current, which is a very important aspect of physics.  Since current is proportional to brightness/functionality of appliances, if the resistance increases, decreasing the current, the brightness etc will go down.  For this reason, some light bulbs shine brighter than others.  It is important to note that there can be no voltage, and therefore no functionality of appliances, without potential difference.  For example, a bird can stand on one power line without being shocked because the current is flowing one way, therefore there is no potential difference and no complete circuit.  If it touches two wires, however, there is potential difference and the bird completes the circuit giving it an electric shock.

There are two types of current:

• Direct Current (dc)- Particles flow in just one direction.
• Alternating Current (ac)- Particles vibrate in different directions.

We then studied electric power.  Electric power is the rate of energy transfer, the amount of energy per unit, and can be found with this equation:

Power = current x voltage

Finally, we learned about two different types of circuit.

• Series Circuit- In series, all appliances are connected one way, if one appliance is unplugged, all others stop working.  This type of circuit uses less current.
• Parallel Circuit- In parallel, appliances are connected so that voltage acts across each one, each appliance completes the circuit.  If one appliance goes out, all others are not affected.  

Given the definitions of each circuit, it is easy to see why most homes and workplaces are wired in parallel.  If  they weren't, all the lights would turn off if one turned off.

We can also see why an entire boarding school dorm may lose energy when girls are getting ready for prom.
Since the building is run on parallel circuit, the more appliances that are turned on, the more current will flow through the system.  When too much flows, the fuse breaks, and the circuit becomes incomplete.

This chapter did not seem to particularly hard.  I found it easy to grasp the concepts, and the problem solving was not difficult because everything used simple equations, such as I = V / R.