Monday, May 7, 2012
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.
hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfie.html
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.htmlhyperphysics.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.
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.
Friday, March 9, 2012
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.
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