Magnetic Fields

Electronic motors are made with magnetic fields.  The magnetic field is between the field magnet and the armature.  These magnetic fields are formed with electric currents or, "the rate of charge flow past a given point in an electric circuit. (hyperphysics.phy-astr.gsu.edu)"  Each magnet has two ends or poles.  These two poles are the north pole and the south pole, each  specific in its magnetic attractions.  Sometimes, one might find that two magnets refuse to stick together.  This is not because they are special, one-of-a-kind magnets rather their two similar poles are being brought closer together.  What this means is that the south pole of one magnet, and the south pole of another with not attract each other.  However, if opposite poles are brought close together, they will attract each other.

The zone of the attracting or repelling poles is the magnetic field.  There are such things as permanent and temporary magnets.  A permanent magnet will continue to hold its magnetic poles, even if it is not in contact with another magnet.  Temporary magnets are objects such as  paper clips that become magnets only when in the region of another magnet's magnetic field.  This is proven thorough the fact that paper clips do not attract each other when by themselves.  The paper clips is made into a magnet, with both of the correct poles.

These magnetic charges are connected to electricity.  Every atom contain negatively charged electrons and positively charged nucleus.  When atoms have less electrons than usual, they become positive (+).  That being said, when atoms have more than the normal amount of electrons, they become negative (-).  Two positive, or two negative, atoms will push away from each other.  Like magnets, oppositely charged atoms will pull towards each other. 

Around 1800, scientists discovered that electric charges were created "when the ends of a chemical 'battery' were connected by a metal wire. (Dr. David P. Stern)"  The charges networked through the connected wire, heating the wire along the way.  This is now known today as electric currents. 

http://www-spof.gsfc.nasa.gov/Education/wmfield.html
hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfie.html

Experiment 10: A Speedy Electric Motor

The notes seen in the two blog posts below are for Experiment 10: A Speedy Electric Motor, on the website:

 http://www.charlesedisonfund.org/

This specific electric motor has four essential parts as explained on the website: the armature, the field magnet, the brushes, and the commutator.  Each of these four parts of the electric motor are key for the motors success.  The better each one is made, the faster the motor will be.

The armature is one of the four parts of an electric motor.  In this specific experiment, it is made up of two 16-penny nails.  The armature is the electromagnet of the motor.  It has magnetic charge once either 22 or 24 gauge magnet wire is tightly wrapped around the two 16-penny nails.  It spins rapidly (depending on the quality of the motor) creating a magnetic field with the appropriately named field magnet.   

The field magnet connects magnetically with the armature to get the motor moving.  The field magnet consists of magnet wire and two L-brackets.  The magnet wire is wrapped around the brackets 400 times, before being secured down.  This part of the motor creates the magnetic field that corresponds with the north and south poles of the armature. 

However, the shaft that the armature is on, and the armature itself, would not rotate without the commutator.  This part of the experiment is difficult, as the aluminum or copper pieces of the commutator have to be soldered to the tips of the magnet wire of the armature. It is important to sand the enamel of the magnet wire before soldering.  If this crucial step is not taken, the motor will not work. 

Lastly, there are the brushes.  The brushes connect with the commutator, and are made up of two pieces of copper-strand wires.  Fanning out the wires of the brushes will make the motor faster, due to the fact that they will cover more of the commutator.  The brushes create a current between the commutator, the armature, and the field magnet.  The brushes take the power from the 6 volt battery, and supply it to the commutator.

This relates back to the post below that explains the difference between motors and engines.  This four-part system is a motor because the energy used to run the system is one of an external source. 

http://www.charlesedisonfund.org/experiments/HTMLexperiments/Chapter5/5-Expt10/p1.html

http://electronics.howstuffworks.com/motor1.htm

Motor Project Notes 1

Motor Project Notes 2

Motors and Engines

The terms motor and engine are commonly used interchangeably, however they do not refer to the same thing (excluding rocket motors/engines).  Motors power electrical machinery, but do so with the help of outside sources of energy.  On the other hand, it is disputed that engines supply their own fuel.  Both fueling systems drive objects that are seen and used every day. 

When describing different types of engines, one can go so far as to mention computer search engines or fire engines.  With the term search engine, the main part of a computer, typically obscured from view, is being referred to.  These engines perform long, detailed calculations and drive the computer accordingly.  The word engine can be derived from the Latin word, ingenium, which as stated in the text, "referred to one's ability to create things, one's native genius... and is also the source of ingenious and ingenuity" (copyrighted to Michael Quinion). 

Simple electric motor from: uq.edu.au



An engine diagram from: submarineboat.com

The word motor descents from the Latin word movere, but unlike the ingenium, this word directly means, "to move" (copyrighted to Michael Quinion).  It was not until the 1850s when the term motor began to refer to moveable objects powered by energy.  The difference between the motor and engine originated around the time when the electrical motor  was first invented.  This motor was very different from the familiar steam engine.  The steam engine was clearly powered by steam, but the electric or hydraulic motor had vague sources of energy.  

http://www.worldwidewords.org/articles/engine.htm

Different Types of Bridges

  The different types and shapes of bridges range from beam bridges to triangle and square bridges. When constructing a bridge, looking into what bridges are the strongest should be the first step.

   The first of three common bridge types is the beam bridge. The first beam bridges were most likely constructed with tree trunks or logs; this assumption was made based upon the origin of the wood. If using piers, we should decide how tall they should be and take into account what is going to move below the bridge. For the span of the bridge, the strength, weight, and the length of the beams used will control how long the span of the bride is. The thicker the material, the greater weight the bridge will hold as well as the longer the bridge will span. However, the larger the beam is, the heavier the bridge is.  So one aspect must be compromised for another.

    A different kind of long spanning bridge is a cantilever. This type of bridge is similar to the lever bridge. In a cantilever bridge, the two ends of a bridge are secured to the ground.  They would act similar to two connected diving boards.  In a cantilever bridge, the inner, center beam would be laid across these diving boards with the ends supporting it and keeping it aloft. These bridges are designed to cross large bodies of water.

   The second type of bridge is the suspension bridge. These bridges are able to use tension to stay together and can span the longest of all bridges. Unlike most bridges, the suspension bridges pull in a sense instead of pushing. These bridges are very pliable and often sway. This is okay as long as it is not in sync with the wind. The swaying could leave the bridge breaking if the wind picks up. 

http://www.sciencetech.technomuses.ca/english/schoolzone/Info_structures.cfm

http://science.howstuffworks.com/engineering/civil/bridge7.htm

Tips When Building Bridges

When building a balsa wood bridge it is important to keep a few things in mind. In order to get the best results out of the bridge, we should follow these simple tips. They will make the bridge stronger and work with the light balsa wood.

The glue used to keep the bridge together is very important. Balsa wood is porous, and due to this, glue that stretches out when its drying is the best that can be used. Gorilla Glue and Probond meet the criteria. However, they will both increase the weight of your bridge more than other glues. When building a bridge, it should be remembered that a lot of glue is unnecessary. It just needs to hold the pieces of the bridge together, such as a joint.

Every piece of wood has a grain, and balsa wood has two very different types. On some balsa wood, the grain is thinner and almost reaches from one end of the cut to the other. This is favorable if there will be a lot of tension on the bridge. The second type of balsa wood has very short grain lines. It is best to use this when we are dealing with compression. This type of balsa wood is stiffer than the first.

Another tip is to keep the bridge in as dry of an environment as possible. The humidity can make your bridge heavier. When using the glue, try not to overload it onto the bridge; a small, simple amount will do the trick. All the while, make sure our hands are relatively clear. The oil on our hands can ruin the glue job, especially on the joints.

If we have enough balsa wood, try to make more than one bridge. With more bridges, we can see the weak points in each and relate that to our final bridge. Also, make sure to add lateral bracing when planning out our bridge. Lateral bracing prevents the bridge from turning, or twisting.

These tips are simply pointers and are not completely necessary. Although, they should be taken into consideration when we are building a bridge, because they will certainly help you make a stronger one.

http://www.garrettsbridges.com/building/25-bridge-building-tips/

http://www.garrettsbridges.com/building/balsa-wood/

The Basics In Building A Bridge

  When building a bridge, we should consider all the possible types we can make. There are different spans, trusses, and girders we can incorporate into our design, and each has their own strengths and weakness, some more than others. The first step before considering designs, however, should be to identify what the bridge will have to hold, or the use of the bridge, and in what circumstances.

  The four principal terms employed when defining a normal bridge are span, material, the position of the roadway regarding the construction of the bridge, and form. Each term has subtopics that leave us many options with the bridge.

  The first term is span; there are three main types of spans, and these can be made with many different things. The three things are beams, girders, or trusses.  When dealing with an arched bridge, a continuos hinged or simple hinged span will work the best. A span is the distance between the legs of the bridge.  Spans are horizontal and when the term span is used, it could also be relating back to the construction of the bridge itself.

  The second main part of a bridge is a truss. The truss is the roadway of the bridge. The main types of trusses are deck, pony, and through trusses. A deck truss is used when the bridge is a main street, with traffic and many cars. The pony truss is employed if the builder wants the traffic to travel in the middle of two superstructures. Pony trusses, however, are not crossed like and “X” on the top of the bridge.  The last truss is the through truss. With this truss, the traffic would travel underneath the superstructure. Unlike pony trusses, through trusses use cross-bracing.

  In a bridge, the girder is the framework made to hold up the weight. What makes horizontal girders so strong is their stiffness. With this they are able to brace the vertical weight on the bridge. A girder is usually very thick, and is sometimes made up of more than one beam.  

         To strengthen the girder, haunches can be involved in its planning. In a haunched girders are not straight, but rather arched towards the end of the bridge. The constraint of these bridges is their size. On most bridges, smaller beams are used, because they are easier to move around. With this, the smaller pieces have to be joined together, usually by splice plates. 

http://pghbridges.com/basics.htm

http://pghbridges.com/termsBrg.htm

The Physics of Magnetic Nail Polish

Magnets play a key role in the newest and most popular fashion sensation.  The results of the innovative magnetic nail polish are largely accredited to the physics of a magnetic pull.  In most cases, you apply two coats of the nail polish.  The first is left alone and then the second coat is heavily applied once the first application has dried.  Before the second coat dries, you hold a  magnet over your nail for about ten seconds and the results are shown below.

Photo taken from: http://www.thelooksforless.com/2011/09/12/manicure-mondays-layla-magnetic-nail-polish-review-tutorial/

            The appearance of this nail polish changes based on the magnet used.  This is because each magnet has differently arranged atoms.  Although the nature of a magnet is not completely understood, scientists believe that each of the millions of atoms that make up a metal have their own separate magnetic charge.  Magnets have both north and south poles.  The magnets pull towards each other when opposite poles are facing each other (north and south), but when the same sides of two magnets are pointed together (such as the two south sides), the magnets will refuse to come in contact.  The atoms of an unmagnetized metal are facing in many different directions.  In a magnetized metal, all the atoms are pointing in the same direction.

Copyright Explain that Stuff 2008, available under Creative Commons Attribution-Noncommercial-Share Alike license.

            Iron is not an initially magnetized metal, but if held up to a magnet, it will turn into one itself.  When the south end of a magnet is held up to iron, the north end of the magnetic atoms inside of the iron material will pull towards the magnet. This reaction makes the iron magnetic, and is seen in the magnetic nail polish. 

            The nail polish contains iron powder with minuscule iron filings, each of which is turned into a little magnet. They either repel or attract the original magnet and each other.  The filings inside the nail polish are what create the unmistakable pattern.  They move around each other until the magnet used is removed. The magnet applied, the arrangement of the powder, and the position of the magnet above the nail will generate a slightly unique pattern. 

http://www.physicscentral.com/explore/action/nailpolish1.cfm