We hear that matter expands when heated and this expansion is not always linear. We also know that alcohol and mercury were initially the liquids used for the construction of thermometers. Clearly, not all thermometers are built this way, but because they are the most common, we’ll start them: the thermometers of this type consist of a glass tube with an inner diameter very small (capillary) soldier a glass sphere containing the liquid selected. The more liquid, the expansion of warming is more noticeable and therefore the rise in the capillary tube, easier to observe.
Surely you have thought that if the bodies expand by heat, it also thins the glass in which is contained the liquid. Will it change the fact the accuracy of the measurement? Dilatation of the glass scale is so small that we can dismiss it, only for very accurate to be used other methods. It is important to consider that for this reason the readings in glass thermometer with an accuracy of 0.01 K.
All liquids freeze and boil at specific temperatures, therefore, each thermometer is designed for specific temperature ranges. In the case of mercury, its freezing point is -39.0 ° C and the boiling point is 356.7 ° C, values ??that limit their range of application. For the same reason, an alcohol thermometer works only in a range from -100 ° C to 70 ° C. Here are the list of some common thermometers
- Gas thermometer
- Platinum resistance thermometers
- Several thermometric probes for use with a digital thermocouple thermometer laboratory
- The temperature inside a furnace is measured with a thermometer or pyrometer radiation
- EXPANSION THERMOMETERS
- Bimetallic strip thermometer
- Thermometers filled systems
- Gas filled thermometers
- Thermometers vapor pressure
- Thermometer pressure steam pressure-sensitive element
- Liquid expansion thermometers
Car fog lights function to boost the visibility for motorists in bad foggy or misty conditions. Fog lights are generally mounted on the front of vehicles, under the hid headlights in most cases. Rear fog lamps are also permitted in quite a few nations, but these folks are not required in North America.You may have ever before mistaken front fog lamps for headlamps. Actually, these two kinds of automobile lights vary significantly from every single other in form, elements and material. A lot fog lamps are spherical in form and include uncomplicated elements. Regular lamps solely have incandescent bulbs or halogen bulbs, where there is no any elective extras; however, much more up to date lamps may characteristic HID, and these lamps consist of much more elements and much more useful to increase the visibility in bad climate conditions.It’s easy for you to upgrade the fog lights into much more luminous HID ones. Aftermarket parts makers present car users with a huge decision of habit HID lights bulbs, all of which is specially designed and forced for specific car make, model and model year. Aftermarket HID burn assemblies normally include HID lights with street-legal color temperature, crystal clear projector utilized for concentrating the burn directly casted to the avenue expanse of the front, and decorative CCFL angel eyes which beatify the complete glance of the burn.Apart from HID bulbs, LED bulbs are also increasingly much more utilized in doing so type of automobile lights. As fog lights are mainly designed for beauty destination in those nations the place these lights are not required, LED burning supply is the optimum ornament for them. LED excels brightly, uses wee power and lasts long. These positive aspects have spurred its attractiveness with car users. At one time LED burning has been mounted on the lamps, amazing beauty effect can happen out.
Perhaps the biggest difference between the 20th century and the 21st is how technology has changed the pace of our lives. We now expect to communicate with anyone on the planet in seconds, not days. We expect the information to us. We expect to be up and walking soon after a hip or knee. Basically, we leave nothing for granted. But that frenetic pace has also changed the way we do business and live our lives. To illustrate this, we want to solve problems immediately, and do not have the patience to find long term solutions. Therefore, we tend to attack the symptoms rather than addressing the real problems, and applying plasters to pacify the moment as opposed to tourniquets which are actually needed. We are satisfied easily solve small problems, as opposed to conquer challenges. Personally, we tend to live for today versus planning for tomorrow. This state of mind that concerns me greatly.
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The technology is an improved road for a target unimproved. The technology is associated with innovation. It involves the transformation of ideas into something useful. Innovation is not just limited to creative people and organizations, but also implies the availability of scientific and technological talent. Technology and innovation are synergistic. Technology has definitely changed our lives for the better.
Looking back in time, we realize how our lives have changed because of the benefits of technology. He provided us with the freedom and less consumption of time and resources. Emphasizing a particular technology for radical changes in his life is just not possible. Economic growth of a country can be measured by the level of technology. This is because a number of factors are responsible for affecting the lifestyle of an individual. The most important factor in deciding how a particular technology is the presence of competition. One type of technology seems beneficial only to a technological advancement does not occur.
The most effective piece of technology is the mobile phone, and now a day being equal to one civilization. Due to technological changes, dependence on technology has increased many folds. Some progress takes place at such a rate that they become self-destructive. The ability to convert carbon dioxide into fuel energy is a revolutionary process, and once well established would change our dependence on non-renewable sources and limited.
Zener diode is having utmost importance in power applications. In zener diode the doping level of P and N type semiconductors are very high as compared to the simple p-n junction diode. When we connect it into any circuit in parallel or series with the equipments in reverse biased, then crossing the certain limit it break down the circuit and the equipment retain safe that is more costlier than zener diode. The whole-sole purpose of zener diode is to provide immediate protection to the equipments which are very sensitive to the varying current and voltage.
In Zener diode we are using two types of mechanism:
(A) Avalanche Breakdown
(B) Zener breakdown
Avalanche Breakdown: In highly doped p-n junction diodes it is occurs, when the accelerated free electrons acquire sufficient kinetic energy to break the bonding among the atoms on bombarding with other atoms and results in regeneration of high number of free electrons moving in the force of electric field. This process causes rapid increase in current in reverse region and known as break down current.
Zener Breakdown: In highly doped p-n junction diodes it is occurs, when the applied electric field increases continuously and reaches to a level, which provides sufficient amount of force on the outer most shell electron. This force is so higher in magnitude, causes breaking in covalent bond among atom and its electrons. This process produces large number of free charge carriers and hence rapidly increases the reverse current.
Application of Zener Diode:
- As a voltage regulator in circuits.
- As a fixed reference voltage in transistor biasing circuits.
- In peak limiters and wave shaping circuits.
- For protection of electrical and electronics equipment.
Tunnel Diode:
It was first observed by Dr. Leo Esaki in 1985, when the impurity level of a normal p-n junction diode is greatly increased i.e. 1000 times more than normal diode its then its characteristics are completely changed. This diode is also known as Esaki diode.
In tunnel diode, the impurity level or concentration is very much higher from any normal p-n junction diode. This amount of concentration makes the depletion layer thin i.e. 10 nanometer of width which is so narrower than normal diode depletion layer i.e. 1 micron of width. In normal p-n junction diode the depletion layer is not crossed by the electron and hole due to lack of sufficient amount of energy. To cross this barrier one may need to increase the voltage around the diode this may lead to burning of diode.
Operating a highly doped p-n junction diode i.e. about one part in 10³ atoms reduces the width of depletion layer i.e. 10-9 meter. Even on applying small amount of voltage the charge carriers can easily penetrate the depletion layer this phenomenon produces a large amount of forward current. The phenomenon of penetrating the charge carriers, directly through the potential barrier, instead of crossing it, is as tunneling and the diode is known as Tunnel Diode.
Application of a tunnel diode:
- As a ultra-high speed switching device. The switching time is of the order of 10-9 sec.
- As a logic memory storage device.
- As a microwave oscillator at higher frequencies i.e. 10 GHz.
Varactor Diode:
When a p-n junction diode using in reverse bias then along depletion layer charge carrier are accumulates massively at the junctions i.e. P and N type regions. In that case, depletion layer behaves as a dielectric to the junction boundaries which are behaving as capacitor plates and holds charge in the form of charge carries. This capacitance is varying on varying the reverse voltage across the diode and the diode is known Variable Capacitor, VariCap, VoltCap or Tunning Diode and Varactor Diode.
The depletion layer decreases when voltage decreases and increases when reverse voltage increases respectively. This leads to change in width of depletion layer and thereby produces variation in dielectric capacity of the capacitor. This phenomenon is similar to simple capacitor in which dielectric layer decreases hence capacitance increases and vice-versa.
In Varactor diode the capacitance parameter is controlled by the method of doping in the depletion layer. Doing on both side of depletion layer is uniform. The range of capacitance varies (tuning range) from 4 to 1 or we can say in the ratio of 4:1 for example the maximum limit of capacitance is 100 pF and minimum limit is 25 pF.
Application of varactor diode:
- Mainly in tuning circuit like radio and transistor.
- In resonance circuit.
The Schottky Diode:
Schottky diode is formed by joining the highly doped semiconductor region (specifically N-type)to metal such as Gold, Silver, and Platinum. It is different from any other diode because in the junction is formed between metal and semiconductor instead of two semiconductor regions.
The reason behind to join a metal piece not a semiconductor is that when the junction voltage gets crossed the limit then a number of large carrier is coming from the metal side to semiconductor region without much increasing the voltage level from the limit. Due to this Schottky diode can be useful in high frequency circuits.
The junction capacitance in Schottky diode is of very low magnitude so that the the operating frequency ranges upto 20 GHz or more than this.
Application of Schottky Diode:
- To rectify very high frequency signals i.e. above 300 MHz.
- For fast switching in digital circuits and also in digital computers application.
- In Transistor-transistor logic circuits.
PIN Diode:
P-I-N diode is made from the joining the three types of semiconductor materials i.e. two heavily doped and one
intrinsic type semiconductor (undoped semiconductor called intrinsic semiconductors). Thus the PIN diode is formed by joining PN type semiconductor separating by intrinsic semiconductor.
The intrinsic semiconductor offers a high resistance to the current flowing through it. The advantage of PIN diode on a normal PN junction diode is s following:
- The capacitance between the PN junctions is decreases because of the increase separation between the P and N type regions. This makes PIN diode a very fast and provide suitable applications in very high frequencies circuits.
- The electron-hole pair generation is much higher than PN junction diode, thus increases the electric field around the P and N regions. This helps PIN diode to process even weak signals.
In PIN diode, the width of depletion layer is controlled by the electron diffusion process across the intrinsic semiconductor region. When forwarded biased is applied across the terminals then depletion layer decreases. Thereby, produces more charge carriers to injected in I region. If the sable bias is applied then it behaves as low resistance device and produces maximum current. PIN diode is working as a variable resistance device.
In reverse biased condition, the depletion layer becomes thick and on increasing the reverse voltage the depletion layer getting thicker till the I region becomes free of mobile charge carriers. The reverse voltage at which this is happen is called as swept out voltage. At this voltage the PIN diode is working as a constant capacitive device.
Applications of PIN diode are as following:
1. In attenuating circuits to control current.
2. In DC controlled microwave operated switch.