Basics of Electricity

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Contents 1 Basics 1.1 Hopefully Review 1.2 Atomic Physics 1.2.1 Some Not-so Basics 1.2.2 What You Need to Know 1.3 Easy Basics 1.3.1 The River 1.3.2 What You Need to Know 1.4 The Power of Electricity

[edit] Basics

[edit] Hopefully Review

• Electricity is caused by the movement of Electrons.
• There are conductive and insulative materials.
  • Conductors allow the flow of electrons.
  • Insulators stop the flow of electrons.
• There are sources that provide electricity.
• There are things that "use" electricity.
• There are Volts, Amperes (Amps), and Watts as well as a myriad of other terms that will be covered.
• Electricity can be deadly but it is helpful on a day-to-day basis.

[edit] Atomic Physics

[edit] Some Not-so Basics

Electricity comes from the movement of electrons between atoms. When an atom gains an electron it becomes more negatively charged, which then pushes away other electrons, similar to the way the like poles of a magnet repel one another. However conductors don't hold onto to that newly acquired electron very well. Think of a row of atoms. When one atom in the line becomes positively charged (because it lost its electron) then another electron is drawn to it. It gains this other electron from one of the other atoms in the conductor, making it a prime candidate for another electron. It continues like a row of dominoes.

When an electron moves it leaves a "hole". This is not an actual physical entity but rather a space-holder that becomes useful in much more advanced electronics. In a piece of conductive material that does not have anything connected to it the process of switching electrons is random and does not cause anything to happen. When a bias, a voltage, is applied to the chunk of material then the electrons will move to the positively charged side of the material, filling holes, but also leaving holes behind. This causes more electrons to move and creates a current. The current is much like a stream and continues to flow until the bias is gone and the material is again equal throughout.

This seems really simple until later on when it is realized that current usually flows in a positive manner from the positive to negative. But as described, the electrons are traveling toward the positive end to balance it out. This is still true and I am not contradicting myself. The flow of electrons is negative because it is a negatively charged particle moving toward a positively charged area. So what is flowing in the opposite direction? The holes are "flowing" in a positive direction, and if it was possible to chart the change in charge of single atoms one would see that as the negative flows toward the positive, so the positive flows toward the negative.

Insulators are simple: Those are stable atoms of elements not prone to losing their electrons. This means they hardly ever share except in extreme conditions that usually cause fires or frostbite. There are also semi-conductors and super-conductors but those have characteristics that we don't need to cover at the moment.

[edit] What You Need to Know

• Electricity flows along conductors.
  • There are electrons that go the opposite way of the current.
  • There are holes, or spaces, that the electrons leave behind that "flow" in the direction of the current.
• Electricity is stopped by insulators.
• There are such things as semi-conductors and super-conductors.

[edit] Easy Basics

[edit] The River

Imagine a nice mountain stream. What does it do? It flows downhill, it falls until it comes to an area of equilibrium. When the water is up at the top of the stream, it has the potential to fall down. If we took away the mountain, it would fall straight down. For those familiar with physics it is the potential energy of the water which gives it this stored energy. In electricity this is the same, although dealing with electrons and concentration rather than water and height. This is still called a potential, but also referred to as charge or a voltage. More mass of water means more potential energy, more electrons means more potential or voltage as well. Charge is actually the quantity of charge of the number electrons/holes around and is usually used in physics, where volts, notated as V, are commonly used in engineering.

When the water is flowing it has a current, and so when electricity flows it also has a current. The faster the flow of water the higher the current, the faster the electrons flow by, the higher electrical current. The electrical term is Amperes which is often shortened to Amps, and notated as A.

In a mountain stream if you cut a straight channel across a bend, the water will soon only follow the cut. In electricity this is called a short, this can be very bad if you are part of this new shorter path to relieve the potential. So always be careful when dealing with electricity. The dangerous part is the current, a static shock between a finger and doorknob has several hundred-thousand volts of potential. A wall socket has 120 V in the US, but the amperage (A) is more than enough to kill.

The metaphor of a stream starts to break down without careful attention to the details to explain electricity. Sometimes the metaphor of pipes is used, although those not familiar with basic fluid dynamics will not see the metaphor too well.

[edit] What You Need to Know

• Concentrations of charge (electrons or holes) results in potential or voltage (V).
• The movement of charge is known as current (A).
• Electricity is dangerous, even in small amounts.
• Be careful with visualizations, electricity can be modeled by several things, but a misconception of one may influence how you learn about electricity.

[edit] The Power of Electricity

In physics a very common problem is figuring out how much power is needed. The same is true for electricity: Watts are a measure of power, the same as horsepower, but the question never arises as to how much horsepower is your sub-woofer? Usually the only time horsepower is mentioned when dealing with electricity is when the electrical power is being converted, by a motor, into mechanical power. Don't worry about equations yet, just know that the power in an electrical system is a combination of the potential, volts, and how fast the current, amps, is flowing.

Return:Topic:Electrical Engineering

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Bgorges 20:50, 6 October 2008 (UTC)