Electricity and Magnetism: Goals 9-21

A magnet is described as any material that attracts iron and materials that contain iron. This, along with the property to attract and repel other magnets and the property that one point of the magnet will always point north when allowed to swing freely, are three properties of magnets. The way magnets interact is simple, unlike poles attract and like poles repel.

            A magnetic domain is a grouping of atoms that have their magnetic fields aligned, creating a magnet. In a magnetized material, all or most of the domains are arranged in the same direction. In a non-magnetic material, the magnetic domains point in different directions. Metals that are non-magnetic can be magnetized by a strong magnet if it rubs on it a couple of times, causing the magnetic field to align and create a temporary magnet.

            The reason that one point of a magnet always turns north when allowed to swing freely is because the Earth acts like a magnet. In the late 1500’s, English physician Sir William Gilbert thought that this was because the Earth’s core contained magnetic rock. Nowadays, however, scientists know that Earth’s core is too hot to be solid, and the temperature is too high to be magnetic. Though Earth’s magnetism is not completely understood, it is known that the circulation of molten material in the core is related to why it’s magnetic.

            Electromagnetism is the relationship between electricity and magnetism. An electromagnet is a strong magnet that can be turned on or off. It is created by wrapping a solenoid (a coil of wire with a current) around a ferromagnetic core. The strength of an electromagnet can be increased in three ways: increasing the current in the solenoid, winding the loops closer together, and using a stronger material as the ferromagnetic core. Whenever there is an electric current, there is magnetism. An electromagnet works when you run a current through a wire surrounding a ferromagnetic core, thus creating a magnetic field. They are used in driving motors, telephones, computers, junkyards, circuit breakers, etc.

            The two types of currents that are used to power our everyday living appliances are DC and AC. As the abbreviation suggests, DC stands for Direct Current and AC stands for Alternating Current. Alternating Current switches direction every half turn, while Direct Current keeps going in the same direction. DC currents are used for many electrical appliances such as computers, but our power sources supply AC currents. To be able to change AC to DC, we need a transformer.

            Transformers are used to increase or decrease voltage. Transformers work with two separate loops of wires wrapped around a metal. If you want to increase the voltage, the secondary coil (output) has to have more loops. Therefore, if you want to decrease the voltage, the secondary coil has to have fewer loops. Transformers are very important in power grids. It is because of transformers that energy has enough power to reach our homes. When electrical energy is transferred to our houses, power grids use step up transformers to increase the voltage in order to transport it, and then, once it gets to our houses, step down transformers are used to bring it down to our everyday voltage, usually 110 or 220.

            A question that is commonly pondered over is whether 110 or 220 voltage is better. It is usually argued that 220 is better because it is more powerful. Though they are alike, 110 voltage and 220 voltage have some differences. Because of its greater power, 220 voltage can function with equipment that requires more effort or intense work, such as a dryer or washer. However, also because it is so powerful, it can lead to overheating quicker than 110, and the extra energy is not needed most of the time for simpler electronics. Despite its negative aspects, 220 is usually the better voltage.

Motor

            Motors and generators are somewhat opposites. A motor transforms electrical energy to mechanical energy whereas a generator transforms mechanical energy to electrical energy.  In a simple motor, the AC current in the coil is transferred to the commutator through the brushes. The current is transferred to the armature, which lies in a magnetic field, and is constantly trying to stay aligned with the magnetic poles, turning the commutator along with it.

There are two types of generators, AC and DC. An AC generator works with a crank. As you turn the crank, the armature in the magnetic field rotates, causing one side to move up and one side to move down. This induces a current in the wire. As the armature turns, slip rings, which are attached to the ends of the armature, turn with it. As they turn, they make contact with the brushes, which can be connected to the rest of the circuit. A DC generator is much like a motor, except, instead of supplying electrical energy to the motor, you spin the motor to produce electrical energy.

AC Generator

Certain precautions need to be taken when dealing with electricity. For this reason, ground wires, fuses, and circuit breakers are used. Ground wires are important because they act as a backup wire in case a neutral wire fails, sending the electricity to the ground, and lowering the risk of electrical shock. Fuses and circuit breakers are used to interrupt the continuity of a circuit in case it overheats and becomes dangerous. The way that they interrupt the circuit, however, is different. In case of emergency, fuses, which are usually made up of metal wires or filaments, melt to stop the flow of electricity. In contrast, circuit breakers usually work with an electromagnet, that when the current reaches unsafe levels, the force of the electromagnet becomes so strong that a switch is flipped and the current breaks.

Electrical energy is something that we are lucky to have in our daily lives. There are however, some advantages and disadvantages to electrical energy. Some advantages of electrical energy are that it is clean, cheap, safe (if used right), and convenient. Some disadvantages of electrical energy is that it is expensive if you use it for heating, and in the case of being at the wrong place, at the wrong time, there is a risk of shocking yourself.

            There are many different methods of power production and distribution. Among them are fossil fuels, nuclear, hydroelectric, biomass, solar, wind, and geothermal. All of these methods of power production either convert mechanical energy or chemical energy into electrical energy. All of these methods have positive aspects and negative aspects. An example would be solar power whose advantages are that it is environmentally friendly, it is a renewable resource, and it saves money; and its disadvantages are its initial cost to set up and build the systems, it is limited to certain locations and climates, and only generates energy during the day time. Another example would be wind power, which even though is in someway eco-friendly, does not produce as much energy or is as stable as the other.

            Power is distributed through cables made from copper and aluminum that are supported by towers in power grids. In the first stages of distribution, electricity is usually transported at about 500,000 volts, and as it gets reduced along the way by transformers, it eventually gets to our houses at our typical, everyday voltage, usually 110 or 220.

Electricity

For the past two weeks, our science class has been reviewing, learning, and investigating the topic of electricity. There have been eight main topics that all students were required to learn, of which included: how charges interact with one another, how charges can be transferred, electric currents, conductors and insulators, how resistance affects currents, Ohm’s law, series vs. parallel circuits, and the difference between voltage, current, and power. The class was divided into groups of three, and each group created a presentation on one of these specific topics.

One of the first things our class did was that we each had to build an electrical circuit with only a battery, a magnet, and a wire. Mine is shown on the video at the side. The point of this project was to make us understand how an electrical circuit works. An electric circuit is a “complete, unbroken path through which electric charges can flow.” The charges in an electric circuit flow from the negative side to the positive side because the electrons are negative. Negative charges repel other negative charges, just as positive charges (protons) repel other positive charges. However, positive and negative charges attract, which is why the electrons flow towards the positive side. In my experiment, the electric current (the continuous flow of electric charges through a material) flowed through the copper wires, through the copper spinner, and back through the other wire. With the force of the magnet pushing the spinner up, and the electricity causing it to move, the spinner executed its task and started turning.

The law of conservation of charge states that charges are neither creates nor destroyed, they are only passed along. Charges can be transferred through three different types of methods: friction, conduction, and induction. When objects are transferred through friction, their electrons move when the two items are rubbed together. In the process of conduction, items can be charged through direct contact, in which electrons transfer from the item with more negative charge to the item with more positive charge.  In the last method, induction, objects do not have to touch to transfer charges. It is caused by the electric fields of the objects, which either attracts or repels electrons.

The next topic is based on conductors and insulators. Conductors help ease the flow of electricity, and its atoms contains electrons that are loosely bound together. Good examples of conductors are silver and copper, like I used in my project. An insulator slows down the flow of electricity, and its atoms are tightly bound together. Good examples of insulators are plastic and rubber. Rubber is usually found wrapped around wires. This is so that when people touch the wires, they don't get shocked.

The fifth topic that we learned was about resistance. Resistance is how difficult it is for charges to flow from materials. There are four things that affect resistance: heat, material, width and length. Take, for example, two cables. One is wide and the other one is half the width, the wider cable will allow more energy to flow than the latter. In some cases, resistance is a good thing. With hairdryers, showers, etc., resistance is needed to produce the friction that causes the heat.

Ohm's Law states a simple equation, Resistance = Voltage/Current. In Ohm's Law, the greater the resistance is, the less the current is and vice-versa. Voltage is a difference in potential energy between two places in a circuit. Voltage causes electric currents because the pressure from the voltage will push the current. Sometimes, the voltage may not be enough to push the current, or it might be too much. That is why you cannot put a 220 volt appliance in a 110 volt socket, or a 110 volt appliance in a 220 volt socket. 

There are two types of circuits, the series circuit and the parallel circuit. In series circuit, the current can only take one path through all of the resistors. This means that if something goes wrong and one of the resistors burn out, the resistors that follow it will also burn out. In contrast, parallel circuits have multiple paths that a current can take, so if a resistor burns out, the other continues working. An example is with christmas lights, sometimes one of the twinkly, colorful lights stops working, and all the others behind it stop shining as well. However, if you take the lighting of a house, for example, if one of the lightbulbs run out, the others stay on. 

The last topic is the difference between voltage, power, and current. This also has an equation: Power = Voltage x Current. This means that if either voltage or current increases, so does the power.

This is basically what we've been talking about since school started, and it will be the base of what we learn for the rest of the school year. Personally, I don't understand this topic very well, and I am having difficulties. However, I plan to get better, and eventually succeed in understanding all of the topic. 

Electricity Quiz