Electric current

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Man has always been curious about the works of electricity; why a shock occurred at times, why something clung to something else. There were once many theories of why what we now understand as electricity was created  one of the ancient theories being magic. Moving forward in time, it is now understood that the building blocks of electricity are the proton, neutron, and electron. A proton has a positive charge, the neutron has no charge, and the electron carries a negative charge. Now, everything around us is made of matter, which in turn is filled with atoms , and

the atom is where the protons, neutrons, and the electrons thrive. The protons are trapped in the center of the atom, also known as the nucleus, and because of this, the electrons moving outside the nucleus along their orbital - are one reason why electric current occurs. However, there are special types of electrons called free electrons. These come off of their atoms and zoom around, which makes electricity easy to flow through certain materials, such as metals. These free electrons are referred to being electrical conductors, because they conduct electricity  simple. Electricity not only works miraculously in the world around us, but also deep within our human bodys. Electricity flows through our nervous system and directs to our neurons - the building blocks of the nervous system; thus, giving our brain and body power to function properly.

Flow Of Charge And Electric Current

Even though electricity is based upon the negatively charges electrons, many people assume the electric current is also always negative. Actually, in most cases, electricity is a flow of positive charges, but it can be a flow of negative charges, or a mix of positive and negative charges flowing in opposing directions. However, the direction of the flow depends upon the type of conductor being used. The conductors have atoms in them, and as said before, the atoms have the protons, neutrons, and electrons embedded in them, which in turn creates electricity. In terms of our everyday electrical devices, only the proton with its positive charge and the electron with its negative charge are being used. Some sources, such as a text book, state that electricity is made up of electrons, and only electrons. In reality, electrons and protons alike make up electricity, and they carry an equal strength of charge. Now, protons embedded in solid metal, such as in a copper wire, do not flow. An example of an electrical charge that is based on the protons instead of the electrons would be the everyday battery. While the battery is, lets say, powering a flashlight, the flow of electricity is moving through the inside of the battery. The flashlights electrical current seems to be a flow of both positive and negative atoms, and there is no doubt an electrical charge of some sort flowing through the battery to power the flashlight. Yet, no single electron streams through. The real flow of the charge is in both directions within the battery, part of the charge is from positive atoms, and the rest is of negative atoms moving in the opposing direction. Now, do not confuse current with flow. Electric current is the rate of the charge flow past a specified spot in an electric circuitand is measured in amperes. The atoms in a battery can have an absence of electrons, causing a positive charge. Reversing it, if the atoms have more electrons, then it carries a negative charge. A charge flows from one end to the other, and it only flows when there is a potential difference, which is a difference in the voltage (potential), between the ends of a conductor. The charge will flow until the potential levels out, then there is no longer a flow through the conductor. So, in order to keep the electricity flowing, the difference in potential need to remain different. Another term for the flow of electric charge is electric current, and it is measured in amperes. An ampere is simply the flow of 1 coulomb (the standard unit of charge) per second.

Alternating Current And Direct Current

An electric current could be either an alternating current (AC) or a direct current (DC). The main purpose of electric current, AC or DC, is to transfer energy from one place to another without a sound, without a hassle, and without inconvenience, which is exactly what we have achieved. Digging deeper, an alternating current does just that - alternates. The electrons in a circuit move in one direction first and then in the opposing direction and repeats this process over and over; thus, alternating back and forth. Alternating directions of charge is caused by alternating voltages. Many AC circuits have voltages and currents that alternate back and forth 60 times per second, also known as 60-hertz current. Different frequencies are used for different things, and although frequency systems vary by country, most electric power is produced at either 50 or 60 Hz (hertz). However, a low frequency is used for low speed electric motors, such as traction motors for railways, and higher frequencies are used for higher motor speed. Airplanes and space shuttles, for example, use a higher frequency to transmit a larger amount of power to their motors. An advantage of alternating current is its ability to change the voltage of the power, using a device called a transformer, which transfers energy from one circuit to another. This saves companies money by using high voltages to transmit power over long distances. Now, direct current is a bit different and is not used as much as it used to because alternating current is more efficient with high power applications. DC produces a constant flow of charge that only goes in one direction. In order for a direct current generator to produce a constant voltage, there are many different sets of coils making irregular intervals that stop and start (intermittent) contact with the brushes. And once again, the battery proves itself a good example, except this time with direct current. The ends of the battery, or the terminals, have an unchanging positive and negative charge. Since the electrons constantly flow through the circuit in the same direction, from the negative terminal to the positive terminal, it is considered a direct current.

Converting AC To DC

Converting an alternating current to a direct current might be hard to perform yourself, but the concept of how it works is not difficult to grasp. The conversion process from alternating current to direct current begins with inserting a diode , which is a mini electronic device that allows electrons to flow through it in only one direction. The goal is to make the back and forth current flowing through something to only flow in a single direction; thus, converting it to direct current. Lets take a wire that has an alternating current flowing through it, and cut it in half. If a diode is inserted correctly to connect the two wire pieces together, the diode will stop the current from moving in both directions by completely ridding of one direction and only allowing the other. For example, the function of a diode is comparable to a two lane street, cars on one lane flowing south and the cars on the other lane flowing north. A car then gets into a car crash (representing one function of the diode, which is stopping the flow of electric current  in this case, the cars) on the lane flowing south, blocking the entire road. Assuming that the lanes go north and south forever, with no turn offs, the cars flowing south would have to slowly squeeze their way into the lane flowing north. This is where an officer (representing the second function of the diode, which stops the current, then allows it to flow again. Stops, lets flow, stops, lets flow, etc.) comes in and directs how many cars on the lane flowing south can turn into the lane flowing north to begin moving again. Lets assume the officer lets two cars from the south move into the north lane at a time, then stops the next two before letting them go again. Furthermore, a rectifier is a device used to convert AC to DC through a process called rectification. A rectifier can be made up of a series of things, such as a vacuum tube; however, we will be focusing on the diode makeup. Now, dont confuse a rectifier with a diode  a rectifier describes a diode that is being used to convert alternating current to direct current. Of course, in order for anything to work efficiently, a multitude of that product is needed. In this case, what is needed to convert AC to DC is the diode, and a single diode works, but not nearly as well as multiple diodes in one circuit working together. There is something called a half-wave rectification (see Figure 2), and this only requires the use of a single diode in order to work, but can also use up to three. During the half wave rectification process, only the positive or negative half of the sine wave is approved to go through at a time, so the diode will only permit the current to flow only during either the positive or negative part of the alternating current sine wave; commonly used with radios. Another form is the full-wave rectification (see Figure 4), which is more powerful than the half-wave rectification process and uses two or more diodes. During this process, the whole wave is made either a continuous positive or negative output.

Ohm's Law

One day a man named Georg Ohm discovered that the current in a circuit is equal to the voltage passed across the circuit divided by the resistance in the same circuit. In other words, current = voltage\resistance, more commonly seen as I=V/R. It is up to resistance to say how much current can rush through an object. The objects that create resistance are called resistors, which simply control the voltage and current in the circuit -- so if the resistance is high, then the current will be reduced. The nice thing about resistors is that they keep a circuit from blowing up because the resistors keep the circuits from overheating. Furthermore, if the resistance stays the same, then the current and voltage are equal. When the voltage goes up, the current goes up as well. The unit of measurement used for current, voltage, and resistance is called an ampere  one ampere is equal to one volt divided by one ohm (1 ampere = 1volt/1ohm). So four amperes would be four volts divided by one ohm, and so on. Now lets get to the fun part and start calculating values! If you have an imaginary light bulb that is connected to a 120 volt circuit and brings in 12 amperes of current, how many ohms would that produce? Taking resistance = voltage/current, resistance would = 120 volts/12amperes which = 10 ohms. So what happens when you are trying to calculate the current instead of the resistance? You simply re-arrange the formula to suite your needs. You take the regular resistance = voltage/current and multiply each side by current over one. By doing this, you will get resistance x current = voltage, and you want current on one side by itself, so divide resistance through both sides, making the equation exactly what you need  current = voltage/resistance. Given this formula, how much current is drawn by an imaginary microwave that has a resistance of 100 ohms when 50 volts are passing through it? Current would equal 50 volts/100 ohms, which equals .5 amperes.

The Speed Of Electrons In A Circuit

Taking the remote control to the television and pushing the power button makes the television click on instantly. Likewise, when you press the call button on your phone it connects the circuit which sends an electrical signal to the phones processor at almost the speed of light. Since the signal of the button is being sent through the wire quickly, the electrons must be rushing through the wire at the same speed, right? Wrong. It is only the signal that moves through the wire at this speed, not the electrons. When it is room temperature, the electrons in a wire or open circuit have a velocity of a few million kilometers per hour, they produce no current because the motion is completely random and in all directions, and there is no net flow in any one direction. However, when something such as a battery or generator is connected, and the circuit completed, an electric field (the space that confines the electrically charged particles) is established inside the wire at almost the speed of light. Even though the electric field is established, the electrons continue to move randomly. But as the electrons move randomly, they are being pushed along the wire by the electric field toward the end of the circuit. The reason the electrons do not move as fast as the signal does is because the electrons have obstacles in their way -- atoms. These unmoving atoms make the electrons collide into them, which constantly delays the movement of the electrons so that their average speed is extraordinarily slow. Now, the conducting wire acts as a guide for the electrical field lines and inside the wire the electric field is directed along it. The conduction electrons speed up because of the electric field, but before they reach a nice speed they bump into those motionless ions and transfer some of their energy to them in the process -- this is why the wires that carry currents become hot. With an alternating current circuit, the conduction electrons do not make any net progress in any direction. In one cycle the electrons move a teensy fraction of a centimeter in one direction, and then the same distance in the opposing direction. Because of this, the electrons rhythmically move from side to side along relatively fixed positions. So when you call your friend and talk to them over the telephone, it is simply the structure of the to and fro motion of the conduction electrons that is carried to where your friend is at close to the speed of light. The electrons that are already within the wires simple vibrate to the rhythm of the structure.

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