Felipe's E-Portfolio: Em9-21 Learning Goals and Explanations

EM9. I can describe the properties and interactions of magnets.

Magnets are pieces of metal which have a magnetic field around them. They were first discovered in a city in Ancient Greece in a rock called magnetite. Magnets have a north and south pole (these names are only relative and are used only to distinct the two sides). If you place two poles together (north and north or south and south) the magnets will repel each other, however if they are opposite poles (north and south), the magnets will attract each other. Some magnets, known as permanent magnets, exert a force on objects without any outside influence. The iron magnetite, for example, is a natural permanent magnet. Other permanent magnets can be made by subjecting certain materials to a magnetic force. When the force is removed, these materials retain their own magnetic properties. This happens because the domains within the metal have been aligned. Another way that a metal can be magnetized is if you apply a current around the material, for example, by applying a coil around the metal and sending a current through it, this way a magnetic field is created around the metal and it becomes a temporary magnet, these are called electromagnets. The reverse procedure can also occur, magnets can become "demagnetized". This can happen in many ways, for example, if you apply enough force to a magnet or heat, the domains can become unaligned and the magnet may lose it's properties.

EM10. I can describe how the magnetic domains are arranged in a magnetic/non-magnetic material.

In a magnetic material, the domains (regions in which the magnetic fields of atoms are grouped together in the same direction), are all aligned.

In a non-magnetic material which is a metal, the domains are scattered and face different directions.

Materials which are not made of metal do not have domains.

EM11. I can explain the connection between electricity and magnetism

The connection between electricity and magnetism is called electromagnetism. With magnetism, you can induce and electric current, and with electricity, you are able to create a magnetic field. When you move a magnet along a circuit, the electrons in the conductor move; this produces a current in the circuit. This conversion is mechanical (the magnet's movement along the wire back and forth) to electrical (the movement of electrons in the wire). Electromagnets are created by producing an electric current in a wire coiled around a piece of ferromagnetic material.

EM12. I can outline the difference between DC/AC current and its uses.

In an a direct current (DC) the electrons flow continuously from one end to the other. This has a very great disadvantage because once the energy source (battery) runs out, the current stops.
In an alternating current (AC) the electrons move back and forth. The electrons will continue as long as there is an alternating voltage source. Alternating current is considered to be more efficient and is used for higher voltages to carry energy at a faster rate.

EM13. I can explain why the Earth behaves like a magnet and the consequences of it.

The earth has a magnetic field. Scientists are unsure as to why this is but believe it has something to do with the molten rock flowing inside the earth.

The magnetic field of the earth is essential to many processes that happen in our daily lives: compasses interact with the earth's north and south poles (they align with the north pole). The earth's magnetic field also protects us from solar flares, which happen more often then we realize but the magnetic field of the earth deflects the charged particles directed towards us during solar flares. The electrical discharge can be seen at either ends of the earth (northern lights/ auroras).

The colorful lights are produced from interactions between the energy in the atmosphere and the various elements colliding together.

EM14. I can explain the importance of grounding wires and using fuses/circuit breakers.

Ground wires provide a path for the current to take to the earth and this path is set apart from the appliance using the current. Almost all appliances today which require larger currents will have grounding wires (you can tell by the third prong in the plug) because it ensures a greater amount of safety and prevents electrocution. Although ground wires are not essential to the performance of an appliance, it can be dangerous not to have them.

Fuses and circuit breakers prevent too much current from flowing through a circuit.

EM15. I can explain how an electromagnet works and cite applications for them.

Electromagnets are made by having a coil with a current flowing through it (solenoid) around a ferromagnetic material. A magnetic field is temporarily produced. The strength of the field can be determined by how strong the current is or how many turns the solenoid has.

Electromagnets are used every day in constructions sites (to lift heavy metal objects), credit cards, MRIs, etc.

EM16. I can explain how a simple motor works (parts and function).

Motors turn electric energy into mechanical energy. Motors are normally composed of the following parts:

Armature: The armature is composed of two parts which have currents flowing in opposite directions (this is essential in the motor's function). It is attached to the commutator and continuously rotates.

Commutator (split rings): A commutator reverses the direction of the current every half turn.

Battery/ Energy source: The battery provides a voltage source which produces a current.

Permanent Magnet: The permanent magnet interacts with the magnetic field of the current flowing through the armature to cause the rotation (the fields constantly try to align themselves with one another however the current is being reversed, causing continuous motion).

Brushes: The brushes transmit the current to the commutator. They are not fixed on the commutator, rather they only lightly touch it.

As we know, an electric current has a magnetic field. Magnetism is essential in motors. As the current travels throughout the armature, the magnetic field around it becomes stronger and is attracted to the permanent magnet on the other side. This causes the armature to do a half-rotation. Once it has rotated half a time, the commutator is touching the opposite brush which causes the field to reverse and the armature to be attracted to the opposite permanent magnet. This is a cycle which will continue as long as there is a current and is what causes the motor to function and continue rotating. We use motors every day in automobiles, printers, computers, etc.

EM17. I can describe how a generator and a transformer work.

Generators work by turning mechanical energy into electrical energy (opposite from a motor). They use some source of energy (such as the force of a stream) to turn a turbine which will rotate the magnet and produce a current in a wire which be transmitted to other areas.

A generator is composed of the following parts:

Armature: The armature is where the electric current is induced. It rotates between the

Slip Rings: Slip rings are located at the ends of each side of the armature. They are used with the brushes to continuously be conducting current to each brush.

Brushes: The brushes are used to transfer the current. They are not connected to the slip rings, rather they lightly touch them.

Crank (optional): A crank can be turned as an alternative to a turbine to rotate the armature.

After the current has been produced, it must be carried throughout the power grids to reach the buildings and other facilities which will use the electrical energy, but before this, the energy must go through a transformer. Transformers are devices used to change the voltage of the energy while maintaing the same power. They can either be step-up (when the voltage output is greater than the input) or step-down (when the voltage output is less than the input). A step-up is normally used before the current is carried to the power grids, it will increase the voltage (decrease the current, normally by using more coils on the outside than initially) so that the current is utilized at a faster rate.

A step-down transformer will decrease the voltage (increase current, normally by having less coils than initially), this is necessary for reasons such as safety and having the correct amount of voltage for your appliance.

EM18. I can explain the importance of transformers to power grids.

Transformers are needed these main reasons:

-So that energy gets from the plant to the areas where it is needed.

-So that there is enough voltage to make the appliance work.

-So that there is not too much voltage for the appliance.

-Safety

Power grids are used to distribute energy from the plant/ place where it is produced to the area it is needed in.

EM19. I can explain methods of power production and distribution.

There are many ways to produce power:

Hydroelectric: Hydroelectric power is produced from the movement of moving water. The natural flow of water will turn a turbine as it flows, the turbine will be connected to a generator which will generate a current and transmit the it to the power grids to be distributed. Hydroelectric energy production is, for the most part, clean and safe. It produces very large amounts of power and can be controlled easily. Downsides to this method of power production include the mass amounts of concrete needed to build a dam, some species living in and around the stream may be affected, the dam can potentially be dangerous if it were to break or when handling to much water (flooding) and their are limited areas for where a dam can be built.

Fossil Fuels: To harvest energy from fossil fuels, the fuel (mainly coal) is burned. The burning coal heats up water which produces steam. The steam turns a turbine which will power the generator and export energy from the plant. Fossil fuels produce mass amounts of energy, however there is an enormous environmental impact. Fossil fuels are non-renewable resources and produce an enormous amount of CO2 emission. These energy facilities are convenient because they can be built virtually anywhere, however an alternative would be much safer for us and our planet.

Geothermal: Geothermal energy comes from the natural steam power exerted by the earth. The steam rises and turns the turbine which powers the generator to transfer the mechanical energy into electrical energy. The power then goes through a transformer and is distributed through the power grids. Geothermal power is natural, safe, produces lots of power, doen't produce waste and is free, however, it can't be controlled and is unpredictable. Also, there are limited places for where you can build a geothermal power plant, however, places like Iceland are almost entirely powered by geothermal energy.

Wind: To harvest energy from the wind in order to produce electrical energy, natural wind turns a blade which will rotate the turbine. The turbine powers the generator which converts the mechanical energy to electric energy. Wind energy is clean, safe, free/natural, and produces a relatively large amount of energy. The only real downsides to wind energy would be that you can only build windmills in some areas, you can't control how much wind there is at different times and they can be lethal to birds.

Solar: Solar energy is turned into electrical energy by specially designed solar panels. Solar energy is very eco-friendly and produces a good amount of energy. On the other side, solar panels (today) are very expensive, the will however, eventually, pay for themselves. Solar energy is not constant (during the night time or on cloudy days) and, with our current technology, cannot be kept for long periods of time and, for this reason, cannot independently power a city.

Nuclear: When you split an atom or create various chemical reactions, tons of energy is produced; this is nuclear energy, but all this comes with a potentially enormous cost. In nuclear energy, the reactions will heat up water to produce steam which will spin the turbine in order for the generator to generate a current to be distributed by the power grids. Nuclear energy produces low amounts of CO2 and a LOT of energy is produced, however there seem to be many more disadvantages: nuclear energy can be very dangerous (explosions can easily occur, such as we've seen in Japan), nuclear power plants can only be built somewhere with a large body of water that could cool down reactors, water is heated up which kills various life forms living in the water, nuclear energy is expensive and it produces highly toxic nuclear waste (from uranium).

Biomass: To produce electrical energy from biomass, organic material is burned and used to heat up water. The boiling water produces steam which spins a turbine that powers a generator which will supply energy to the power grids to be distributed. Biomass energy production is, for the most part, safe and eco-friendly (as you are only burning organic material) and these types of plants can be built anywhere. Biomass energy, however, requires very large amounts of organic material to create sufficient energy, for this reason, this type of energy production is uncommon because it is not very efficient.

After the electrical energy is generated, it will go through a transformer to increase voltage, then the current will be transmitted through power lines until it reaches the area where it is needed, go through another transformer to adjust the voltage, and be used by various appliances.

EM20. I can describe the differences of 110v/220v and main advantages and disadvantages of each.

220 volts are more efficient but not as safe. As the voltage is higher, the energy is transmitted more quickly and with less resistance and allows for less energy loss and less heat up. Many places such as the majority of South America, Europe and Asia use 220v. 110 volts transfer energy at a slower pace. More energy is lost and there is a larger chance of an appliance over-heating because of this. The majority of North America uses 110v.

EM21. I can describe the advantages and disadvantages of electrical energy.

Electricity is used to power a tremendous part of today's technology. We use it every day in numerous situations. It allows us to power buildings and homes but normally comes with a cost; our environment. To produce electricity, we burn precious natural resources, negatively impact our environment and even directly jeopardize our safety at times.