Month: June 2016 # Electric conductivity

Electric conductivity

06/30/16

“What are the properties of materials that conducts electric current and how can we measure it?”

When pondering electrical insulators, many may wonder if there are any anti-thesis to such materials? Specifically, what are some properties of objects that conduct electricity? And how do they do so? First off all, we must think about how electric current works in the first place. Electric current is caused when a voltage potential difference interacts with the free-moving electrons within a lattice. These particles, being weakly bonded to their structure, are carried away in the direction of the potential difference. So logically, all current conducting materials (which will henceforth be referred to as conductors) must have an internal lattice with electromagnetic bonds that are not too powerful, and a path for electron travel.

With this knowledge, we can then delve further in to what geometric factors may affect the conductivity. If the cross-sectional area of the object is larger, then that means that the electrons have a greater area to travel through (remember, electrons do not move in a straight line, they bounce around the internal structure, so when the area gets wider, they have more room to move, which means less traffic and therefore less collision and therefore less resistance). Secondly, if the Length is longer, then there will be more internal resistance, which would lead to a slowdown.

After much research, scientists and engineers have come up with an analytic model of conductivity, with the equation G=(alpha)*A/L, with G being the capacitance, (alpha) being a constant, A being the cross sectional area, and L being the length. What’s even more interesting is that this relationship is directly inverse to the equation for  resistance! This is an amazing technical feat, because this means that human ingenuity was able to find a fundamental relationship between the resistance and conductivity of a material. # Electric insulators

Electric insulators

06/29/16

“How do we classify materials that do not let charge flow freely?”

For most of our study of electromagnetism, we have been studying materials that allow electrons to flow freely. But out of curiosity, are there materials that do not allow such a free movement of electrons? If these materials do in fact exist, then trying to induce an electric current to flow through them would be futile, as the electrons would not even budge. Believe it or not, these objects do in fact exist, and scientists and engineers  classify these materials as insulators. Insulators have many pragmatic purposes, such as dielectrics and high voltage systems. # Electric polarization

Electric polarization

06/28/16

“Do insulators respond to electric fields?”

What happens when an insulator, which by nature holds it’s charges in stasis, is placed within an electric field, specifically one with a very large strength? Well, as an object within the universe. the insulating material is made up of subatomic particles. Some of these subatomic particles have a charge.The charges will react to this electric field, and consequently, particles of one charge will be attracted to one side of the object, and particles of another charge will be attracted to another. As a result, the object will have an induced polarization, or some parts of the object’s geometry will have a net charge as a result of the electric force. # Dielectrics

Dielectrics

06/27/16

“Is there a way to increase the capacitance of a capacitor without actually modifying the capacitor itself?

Scientists and Engineers are very practically minded people,so when working with electronics, they would like to make the components as efficient as possible. So when applying this mentality ro capacitors, one way to accomplish this is by increasing the capacitance of the capacitors themselves. So let’s think about how a capacitor works in the first place. If you remember, what makes such components function is that two conducting plates are placed parallel in between a non-conducting material. Let’s call this material a dielectric. When placed in between the two charged plates, this dielectric will react to the net charge on each plate and become polarized. As a consequence, some of the negative charge of the dielectric will be oriented towards the positive plated and vice versa for the negative plate. This causes some of the charge to cancel out, which reduces the effective voltage, which increases the space for extra charge which allows the capacitor to store more charge! We can symbolically relate the old and new capacitance with the equation C=kc, where the capital C represents the new capacitance, k representing the dielectric constant (basically the quantity of the material to store energy in an electric field) and c representing the old capacitance. As one can see, dielectrics are very practical devices that can have many potential uses # Supercapacitors

Supercapacitors

06/26/16

“Are there capacitors that can store much more energy than average?”

Let’s think about something. With the advancement of technology, new ways to store sufficient energy for machines needs to be introduced. One way we can do that is by identifying an existing concept and modifying it suit our needs. Let’s take capacitors. they’re simple, useful, and have a lot of potential for applications. One of the main bottlenecks with capacitors is that they can only store so much energy. Specifically, most capacitors are rated in Microfarads, (one farad = charge/voltage, or the ratio of charge to voltage). This means that with a certain voltage only a very tiny amount of charge can be stored (specifically, one microfarad means that it would take one million volts to store one coulomb of charge).

Now, how could we modify capacitors to store a higher density of charge? Well, as discussed earlier, the capacitance of a capacitor is proportional to the area of the plates divided by the distance between them, so what if not only we used special materials, but we also used very large plates separated at a very small distance? Scientists and  engineers have termed such an invention supercapacitors. Supercapacitors can have capacitance values usually rated in the farad level, or one million times the ratio of noraml capacitors! This means that such inventions can store much more energy than.Supercapacitors (also known as ultracapacitors) have many applications, ranging from being used as a storage medium for regenerative braking systems to Defibrillators. In fact, supercapacitors are deemed to be so practical that major that major transportation networks such as the Portland MAX are starting to use them # Practice of Capacitors

Practice of Capacitors

06/25/16

“How can we apply capacitors to accomplish practical tasks?”

Capacitors have many uses in application. The most common utilization for capacitors is to store energy. Energy can be stored within the electric field of a capacitor, and this energy can continue being stored even if the battery has been disconnected! Capacitors also have a very quick discharge time (often only in the milliseconds) so they can serve as a quick battery. Capacitors can also be used a sensors, accomplishing tasks such as measuring the fuel levels in an airplane. However, one of the most powerful uses of a capacitor is to be a low pass filter. Since the resistance of capacitors in an AC circuit increases inversely proportionally to the frequency of an object, a low frequency current will be hampered by the filter, which means that a minimum threshold of frequency must pass through. # Theory of Capacitors

Theory of Capacitors

06/24/16

“Is it possible to store electricity in an electric field?”

Let us consider the following. Two conductive plates are placed on the positive and negative terminals of a circuit with a battery, both in parallel with one another and separated by an insulating material. When the battery turns on, electrons will rush from the “positive” terminal plate, causing a net positive charge on the aforementioned plate. This net charge will then induce electrons to flow from the negative side of the battery to the other plate The balance of these two charges will create an electric field, which in turn will store voltage. This device is called a Capacitor

We can symbolically analyze capacitors using the equation C=qv, with C being the capacitance, q being the charge, and V being the voltage. Now let’s think about this equation from a real world perspective. We know that Capacitance is caused by a charged particles emiting voltages, so the higher the ratio of maximum charged particles to voltage, the more that this capacitor can store. An equivalent  way to put this equations is C=e*A/D, where e is the electric permittivity constant, A is the area, and d is the distance between the plates. Again, let’s put this in a real world perspective. This seems to be a ratio of the area of the plates to the distance between them, so the more area, the more charge we can store, and the greater distance the smaller the electric potential will be between the charges In addition, we can analyze the energy of the capacitors using the equation E=½ * C* V2, so the more capacitance and voltage, the more energy can be stored in in the object. In summation, capacitors are an intriuing way to store energy