how does a light emiting diode work?
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go to www.howstuffworks.com\nu'll find ur ans there...\ngd luck!!
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In a typical 'flashing LED' circuit that uses a capacitor. NORMALLY it will SLOW the frequency of the flash as it takes longer to go through a charge/discharge cycle.\n\nOther circuits that use capacitors for flashing LED can induce a 'decay' in the switch off if using an I.C ('chip') as the timer resulting in the light fading out gradually after each cycle.
605008
In a p-n-p diode, the base is n-type and the emitter is p-type. If you forward bias the transistor, it means that V_base < V_emitter (e.g. V_base = 4.3V and V_emitter = 5V). Since the emitter to base is just a p-n diode, you expect such biasing will give you a forward current as in a p-n diode. That means current flows from the emitter to the base.\n\nHowever, if you really want to understand the source of the current, you have to use the concept of electron and hole. (Let me know if you don't know what is hole http://www.kodkodkod.com/index_files/submitquestion.htm). In a p-n junction, holes are injected from p to n and electrons are injected from n to p. They together contribute the the current. Similarly, in a p-n-p transistor, the holes from the emitter are injected from p-emitter to the n-base and electrons are injected from the n-base to the p-emitter. However, most of the holes from the emitter cannot be "collected" by the base and indeed they are "collected" by the Collector. That's why you find that I_E and I_C >> I_B. Therefore, the base current is basically due to the electrons from the base.\n\nOf course, in a non-ideal transistor, some holes from the emitter are collected by the base and there is also reverse current between the base and the collector. As a result, the base current is a summation of all the aforementioned components.\n\nI think my answer might not really tailor-made to your need. It's better to let us know how much you know about the transistors (or your education in EE). The answer to the same question you ask can be very different from high school to research level. Let us know if you need more help!\n\nKodKodKod Learning Consulting - http://www.kodkodkod.com
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Lights in your car interior require little energy and are used rarely and in shorter time periods than most bulbs.  They do burn out though.  \n\nLEDs, the source of light for your cellphone (well, some phones), are much more energy efficient since the light is created from a different process compared to a bulb (light bulbs are essentially resistors that heat up and release light).  LEDs last 5-20 times longer than conventional bulbs, and thus are the future.
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a diode blocks current from flowing in a certain direction. current will flow from the non striped side to the striped side
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In an electric torch the bulb glows when we switch on the circuit and bulb glows off when we switch off the circuit. \n\nGlowing of bulb is the indication that the current is in the circuit. When there is no current the bulb will not glow.\n\nWe use the cells (Battery) as long as it has life.  The cells have electric energy and they are used when we want. When it is not used, (switch off position) there is no current in the wire connecting the bulb.\n\nThe differences between this and the power supply through lines to the buildings are not much.\n\nIn the latter, instead of direct current, alternating current is used; instead of small power huge power is used.\n\nTherefore when the switch is in off position there is no current in the lines, but they are full of energy and at any time they can produce current when the switch is on.\n\nAn analogy with water tank may be useful.  Water is stored in the tank. Whenever we open the pipe water flows in the whole pipe connecting the tank and the end pipe, when we close the pipe no water flows but water pressure will be there.
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Solar cells work on the principle of the photoelectric effect. If you are not familiar with it, the photoelectric effect explains why when light shines on a metal plate, a current is created. It is because photons in the light displace electrons in the metal. When the electrons are displaced their movement creates a current. It is this effect that allows solar cells to generate electricity:)
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attach a light bulb to a battery and have current pass through the different cups, the more current the brighter the light.
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I would probably use Light Emiting Diodes connected to a low voltage dc source using very small gauge twin-lead wire.
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Actually, If you shine light on a steel door, the atoms that make up the surface of the door will absorb the photonic energy, and if they absorb enough photonic energy, they will emit the energy. Sometimes the newly emitted energy is outward away from the door, and sometimes the energy is emitted inward and propagated to atoms further into the doors structure.\n\nTo make thing more complicated, the energy is only emitted as photonic energy sometimes, when the atoms have the right amount of energy built up to release a quanta of photonic value. Other times the energy is emitted as heat energy. \n\nThe door is trying to propagate the photonic anergy through to the other side, however the atoms that comprise the door are capable of retaining a great deal of energy, and when they do release it, based on quantum mechanics, there is only a probability that it will be directed into and not out of the door.\n\nIf you quickly heat the atoms in a specific region ,(fill them up with energy), without giving them time to transfer the energy away, (blow torch) you can see the glowing red door on the other side.\n\nIn short, it is due the the energy retention strength of the atoms that make up the solid.
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a regular light bulb \nas apposed to a floresent
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with the aid of a ballast which controls current to each side of the bulb and the bulb is filled with a luminescent gas that when heated will illuminate
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Old flourescent lamps needs a starter switch because flourescents bulbs are made of enclosed mercury, argon and phosphor. Electrical current can flow freely through the tube but it will not light up. When you hit the starter switch it produces an arc, then electrons collide with the atoms and other gases to produce a plasma. Today, we have the rapid start lamp. Same principle, but it doesn't have a starter switch. Instead, the lamp's ballast constantly channels configured current flow resulting a voltage across the tube to heat up electrode filaments very quickly, boiling off electrons, which ionize the gas in the tube. Then the voltage difference between the electrodes establishes an electrical arc to turn on flourescent lights.
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An infrared LED is a light emitting diode that emits light in the infrared portion of the spectrum.  Infrared LEDs are commonly used in remote controls.
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First, take the bulb out of a flashlight.  Carefully remove about an inch of the plastic covering on both ends of two one foot lengths of wire.  Attach one bare end to the bottom of a D-sized battery (good tape might work).  Attach the other end of this wire to the SIDE of the metal part of the bulb.  \nAttach one end of the other wire to the top of the battery.  And attach the end of this wire to the bottom of the bulb.\nThat should do it!
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These are specially designed light bulbs that have had their light output calibrated to a standard source at NIST (or maybe some other standards organization). They must be operated at a specified voltage potential. They usually cost an arm and a leg, have a limited lifetime (the filament evaporates over time changing its characteristics and also plating the glass of the bulb with a thin film of metal) and are only as stable as the voltage/current supply you power it with. You must also take care to never touch the glass with bare skin or anything else that might deposit contaminants.\n\nYou also have to be very careful not to touch the glass with bare skin or any other contaminants.
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An electric INCANDSCENT bulb uses a tungstene filament (twisted wire) that is heated by the current passing through to several hundred degrees.  It is this heat that heats the glass.  It is also the proof of inefficiency of the bulb, because it is transforming 80% of the energy it receives into heat, giving only 20% for light!\nIn the FLUORESCENT tubes, the light is produced by the ionisation of the internal gas (neon or argon).  This ionisation is initiated by heating two small filaments at teach end of the tube, that heat up a small drop of mercury.  Once the mercury is vaporised inside the tube, the "starter" opens, creating a high voltage puls across the whole tube, ionising the gas that then becomes conductor: a small current passes through the gas, and the filaments are disconnected.  Since the ionised and conductive gas has nearly no resistance, the current is limited by the "ballast" (an inductor inserted in series).\nSince the CURRENT is limited, there is no "Joule Effect" (heating) and the tube stays pretty cool.\nTheir efficiency is about 100 times more than a bulb... (in terms of power/light ratio).