Porcelain

Porcelain is a ceramic dielectric. This was the first ceramic material to be used by the electrical industry. Porcelain is impervious to moisture, resist atmospheric conduction attacks and when glazed, surface become too smooth which is easily cleaned. The basic composition of porcelain is 50% clay, 25% feldspar and 25% flint. The quality of the final product and its degree of vitrification depends upon the fineness of grinding, the method of forming and the annealing temperature. By varying the proportions of three main ingredients it is possible to emphasize certain properties such as heat, shock resistance and dielectric strength or mechanical strength. We can broadly classify porcelain materials into two: Impervious high tension porcelain and porous low tension porcelain.

Factors influencing acoustic properties of buildings

In a building, the seats should be arranged such that they are along the circumference of an ellipse whose semimajor and semiminor axes bear a ratio 4:3. Walls should have an optimum reflecting power. Better you keep a parabolic reflector at the back of speaker with the position of the speaker at the focus of the reflector. Reverberation time should have an optimum value. To minimize echelon effect, always make steps of unequal width and cover them with some suitable absorbing material. Mufflers can be used to reduce the sound from systems containing a noise source connected to a fine pipe or suitable duct system such as air conditioning systems, fans, industrial blowers, gasoline and diesel engines, compressor and jet engine inlets and exhausts. There are two types of mufflers- reactive and dissiapative.

Vacuum science and technology

The meaning of the word ‘vacuum’ is ‘emptiness’. i.e., a space without any matter. So in vacuum, the space will have no air and other gases. Usually vacuum means a space where pressure is less than 760 Torr. How to generate vacuum? One way is just similar to the suction in an ordinary drinking straw. Here we reduce the pressure on the liquid surface inner region of straw relative to the pressure above the liquid in the drinking cup. The extra pressure which is responsible for pushing the liquid into the straw to reach the liquid in our mouth. The boiling temperature of any liquid becomes reduced at vacuum. Electrical discharge phenomena of gases lead to the discovery of electrons and X-rays. For this vacuum condition is a must and that is the importance of vauum science in the technological area.

Cathode ray oscilloscope (CRO)

This device is electronic and used by researchers as well as students all over the world. If we have to analyze electrical signals we usually depend upon cathode ray oscilloscope. Physics researchers especially those who are carrying out magnetic materials research, rely on cathode ray oscilloscopes to draw magnetic hysteresis curves of feroomagnetic, antiferromagnetic and ferromagnetic materials. A pulse which is proportional to applied magnetic field and a pulse which is proportional to induced magnetic flux density or induced magnetization is fed to input of cathode ray oscilloscope. As a result of these we obtain a loop from which we can easily note down saturation magnetization value, Remanent magnetization value and coercive field.

Display systems

Cathode ray tube (CRT) is the conventional display system of electronic devices. But it is hazardous and consumes more space. So researchers preferred liquid crystal technology display systems. But this one is not economical and resolution was too minimal. So rigorous research started in this field. The common man requires a simple display system with of course advanced technology but that should be economical, risk free and should consume minimum space. Latest technology uses either plasma panel display devices or field emission display devices. Field emission display devices are preferred because of its high resolution and it is very economical. Nowadays display systems with field emission technology are available in the display devices market all over the world with an investor friendly price.

Photometer

Photometer is an optical device which is used to compare the power of illumination or luminous intensities of two light sources. In the market, we can see variety of photometers. The convenient and precise with maximum accuracy can expect from the following photometers-Lummer-Brodhum photometer, Flicker photometer and photovoltaic photometer. The Lummer-Brodhum photometer limits its application to monochromatic spectrum. i.e., it cannot be used when light sources emit different colour light. Flicker photometer is having same problem but in this case accuracy is more. These photometers are also can be used for the verification of inverse square law of light and sometimes as photocell.

Transistors and amplifiers

Transistor is a three terminal two junction semiconductor device. Actually for manufacturing a transistor first step is to select an intrinsic semiconductor, say, pure silicon. The silicon substrate is treated with the process, doping. Doping is nothing but adding of pentavalent and trivalent impurities to pure crystal. If we add pentavalent impurity, that will result in n-type semiconductor. If we add trivalent impurity, that will result in p-type impurity. Two p-type semiconductor and one n-type semiconductor are sandwiched to form p-n-p transistor. Two n-type semiconductor and one p-type semiconductor are sandwiched to form n-p-n transistor. Usually common emitter configuration yields high voltage gain, current gain and good characteristics. Hence this configuration is used for making amplifiers.