RC Circuits: A Guide About Circuits

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                                                  RC Circuit An circuit contains a single resistor, and a single capacitor . From your course textbook you should already know that a capacitor is a two-terminal device whose voltage, , and current, , satisfy the following relationship, This equation says that the current flowing through a capacitor is proportional to the rate at which voltage changes across the device’s terminals. The proportionality constant, is called the device’s capacitance and it is measured in units called farads. Capacitors come in a variety of forms. One of the most common types of capacitors is a ceramic capacitor. A ceramic capacitor is shaped like a disk with two leads coming out of it. A picture of the schematic symbol of the capacitor is shown in figure 1. This symbol consists of two bars (representing the capacitor’s two plates) with two leads coming out of them. A picture of a representative ceramic capacitor is also shown in figure 1. Another type of capacitor is the electrolytic capacitor. The symbol for an electrolytic capacitor has one of its plates curved and the top plate is marked with a plus sign (see figure 1). Electrolytic capacitors are constructed using a paper soaked in an electrolyte. This fabrication method gives enormous capacitances in a very small volume. But it also results in the capacitor being polarized. In other words, the capacitor only works with one polarity of voltage. If you reverse the polarity, hydrogen can disassociate from the internal anode of the capacitor and this hydrogen can explode. Electrolytic capacitors always have their polarity clearly marked, often with a bunch of negative signs pointed at the negative terminal. A picture of an electrolytic capacitor is shown in figure 1. Figure 1: Symbols and drawings of capacitors An circuit is a particularly simple network containing a capacitor. The circuit consists of an independent voltage source in series with a resistor, , and a capacitor . The schematic diagram for this circuit is shown in figure 2. Analyzing this circuit means determining the voltage over the capacitor, , (as a function of time). The exact solution, of course, depends on two things. These two things are the initial voltage over the capacitor, , and the input voltage, , generated by the independent source. In the remainder of this section we state two specific solutions known as the natural response and step response. The derivation of these particular response equations is done in the lecture component of the course. Figure 2: RC circuit Natural Response: The first specific solution we’ll consider is the voltage over the capacitor under the assumption that the capacitor’s initial voltage is and the applied input voltage is zero (i.e., for all...

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Super Capacitor: Invention Charges Phones Instantly

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           Super Capacitor Phone Charger   California teen Eesha Khare was awarded a $50,000 prize at the Intel International Science and Engineering Fair for creating a breakthrough technological device that may revolutionize our experience with mobile devices. The futuristic gadget has the potential to fully charge cell phones in as few as 20 seconds flat. The device, which only so far has been used to power a light-emitting diode, also has the potential to hold the charge longer than current devices, lasting for 10,000 charge-recharge cycles, compared to only 1,000 cycles on conventional rechargeable batteries. Khare believes that it could one day be used to power phones, cars and other equipment. Apparently Google and other tech giants agree, as the young talent has been courted and contacted by some of the worlds’ most innovative tech companies. The California native studied nano chemistry in order to scale down the size of her remarkable invention, and she notes that “it’s also flexible, so it can be used in roll-up displays and clothing and fabric … it has a lot of different advantages over batteries in that sense.” Khare intends to use her prize money to pay for college and work on further scientific advancements. She was the runner-up to a 19-year-old Romanian student, who created a low-cost artificial intelligence that can drive vehicles and tied a with Louisiana 17-year-old Henry Wanjune, who figured out new ways to measure dark matter and energy in space. Khare is Harvard-bound for college, and the minority female student says that she wants to “set the world on fire” and we can only hope that she’s given every tool and opportunity to do just that....

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Contest Entry – The International Challenge on Economic Ideas

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The International Challenge on Economic Ideas (ICEI) is an international essay competition aimed towards undergraduate students from all over the world. ICEI is a nonprofit annual event that is organized by the Economics Student Association of Universitas Gadjah Mada (UGM). All participants are expected to elaborate on the theme  of “Financial Policy to Create Economic Sustainability”. Eligibility This is open to all undergraduate students worldwide.Only individual submission is allowed. Team submission will be rejected. Awards 1st Place: 700 USD + certificate + the Best Essays Compilation book + 10 minutes presentation in the FSDE seminar 2nd Place: 500 USD + certificate + the Best Essays Compilation book 3rd Place: 300 USD + certificate + the Best Essays Compilation book The top three winners will be invited to attend the FSDE International Seminar in Yogyakarta, patient Indonesia, with VIP status and the privilege to talk with the speakers. (Tickets and accommodation will be subsidized by the committee) FSDE Seminar will be held on: Time : Saturday, November...

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Jabir Ibn Hayyan: A Great Muslim Scientist

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                Jabir Bin Hayyan: The Father of Chemistry   Achievements: Jabir bin Hayyan prepared chemicals, discovered many acids, and prepared, as well as, improved many chemical processes. He stressed the significance of experimenting one’s theory, and this is why we see a lot of inventions and discoveries made by him. In fact, he was the one who introduced experimental techniques in the field of chemistry. He gave a detailed description of acetic acid, tartaric acid, and citric acid. Discovery of hydrochloric acid, sulphuric acid, and nitric acid are few of the greatest contributions made by Jabir bin Hayyan. He combined nitric acid with the hydrochloric acid and invented another acid termed today as “Aqua Regia”. The latter is strong enough to dissolve gold. He discovered chemical procedures as significant as crystallization, melting, distillation, calcination, reduction, liquidation, and sublimation. Dyeing of cloth and leather, as well as, preparation of steel are also associated with this great Islamic scientist. His division of substance into three different classes worked as the basis for modern day classification of metals and non metals. He worked hard for devising methods to refine and purify metals. We get to know from his works that he was dedicated towards finding out the individual properties of elements. Preparation of antimony, basic lead carbonate, and arsenic from their respective sulphides also connects back to Jabir bin Hayyan. According to historians, Jabir respected his mentor Imam Jafar As-Sadiq a lot. To fulfil his teacher’s desire, Jabir bin Hayyan made revolutionary inventions including; – A Substance that could rust proof iron surfaces, while waterproof cloth. – A paper that couldn’t catch fire. – An ink which could be seen and read in the dark (at night time).       Books and Treatises: Around 3000 books and treatises are attributed to the name of Jabir bin Hayyan. The topics are diverse in nature; ranging from music, magic, philosophy, logic and metaphysics to chemistry, alchemy, physics, medicine, astrology, geography, and astronomy. The “Book of Seventy” is a collection of his various works like “Book of Venus”. Other noteworthy works of Jabir bin Hayyan include Book of Stones, Book of 112, Composition of Alchemy, Kitaab-ur-Rahmah, and Kitab-ut-Tajmee. His research has been translated to many European languages, and has been used in western educational institutions for centuries. This is why he is called the ‘Father of Modern Chemistry’.    ...

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Series and Parallel Circuits

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                                                           Series and parallel circuits: Circuits consisting of just one battery and one load resistance are very simple to analyze, sildenafil but they are not often found in practical applications. Usually, cost we find circuits where more than two components are connected together. There are two basic ways in which to connect more than two circuit components: series and parallel. First, search an example of a series circuit: Here, we have three resistors (labeled R1, R2, and R3), connected in a long chain from one terminal of the battery to the other. (It should be noted that the subscript labeling—those little numbers to the lower-right of the letter “R”—are unrelated to the resistor values in ohms. They serve only to identify one resistor from another.) The defining characteristic of a series circuit is that there is only one path for electrons to flow. In this circuit the electrons flow in a counter-clockwise direction, from point 4 to point 3 to point 2 to point 1 and back around to 4. Now, let’s look at the other type of circuit, a parallel configuration: Again, we have three resistors, but this time they form more than one continuous path for electrons to flow. There’s one path from 8 to 7 to 2 to 1 and back to 8 again. There’s another from 8 to 7 to 6 to 3 to 2 to 1 and back to 8 again. And then there’s a third path from 8 to 7 to 6 to 5 to 4 to 3 to 2 to 1 and back to 8 again. Each individual path (through R1, R2, and R3) is called a branch. The defining characteristic of a parallel circuit is that all components are connected between the same set of electrically common points. Looking at the schematic diagram, we see that points 1, 2, 3, and 4 are all electrically common. So are points 8, 7, 6, and 5. Note that all resistors as well as the battery are connected between these two sets of points. And, of course, the complexity doesn’t stop at simple series and parallel either! We can have circuits that are a combination of series and parallel, too: In this circuit, we have two loops for electrons to flow through: one from 6 to 5 to 2 to 1 and back to 6 again, and another from 6 to 5 to 4 to 3 to 2 to 1 and back to 6 again. Notice how both current paths go through R1 (from point 2...

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