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Author Archives: admin

Properties and uses of alpha beta and gamma rays

What is radioactivity? In the March 1896 Henri Becquerel announced the discovery of radioactivity similar to X-rays.Although rays (X-rays) had been discovered less than four month earlier it was already known that X-rays come from the fluorescence wall of the discharge tube and thus it was thought that fluorescence and phosphorescence might be responsible for them. Becquerel known that Uranium ...

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Thermal radiation:Definition,examples and properties

Thermal radiation Radiation emitted by such a body due to its temperature is called thermal radiation.All bodies not only emit such radiation but also absorb it from their surroundings.If the rate of absorption and emission from a body become equal ,the body is said to be in thermal equilibrium with its surroundings. The spectrum of thermal radiation from a hot ...

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Can a transformer operate on DC?

A transformer cannot operate on a steady or unchanging dc voltage such as that of a battery.It requires a voltage which rises and falls.Since an ac voltage not only changes its magnitude but its direction as well,it is used to operate the transformers. However,a transformer will operate from dc voltage if this voltage also undergoes changes.Transformers used for audio amplifiers ...

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What is Photovoltaic effect

Photovoltaic effect: An effect arising when a junction exists between two dissimilar materials and one of the materials is exposed to electromagnetic radiation,usually in the range near ultraviolet to infrared.The two materials may,for example,be a metal and a semiconductor or two semiconductors of opposite polarity,the combination forming a Schottky barrier and a P-N junction respectively.A forward voltage appears across the ...

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What instrument is used to measure atmospheric pressure?

  Barometer is an instrument used to measure atmospheric pressure. How can we measure atmospheric pressure by mercury barometer? Mercury barometers consist of a glass tube about 80 cm long,closed at one end.The tube is filled with mercury and then placed,open end downward,in a reservoir of mercury.As the atmospheric pressure changes ,the level of the mercury changes and to a ...

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what is difference between impedence and reactance?

Circuits with capacitors and inductors are more complicated than the resistive circuits we talked about earlier ,in that their behavior depends on frequency:A “voltage divider ” containing a capacitor or inductor will have a frequency dependent division ratio.In addition ,circuits containing these components (known collectively as reactive components),”corrupt” input waveforms such as square waves,as we just saw. However,both capacitors and ...

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Eddy current testing principle

What is eddy current? A current induced in a conductor when subject to a varying magnetic field.Such currents are a source of energy dissipation (eddy current loss) in alternating current machinery.The reaction between the eddy currents in a moving conductor and the magnetic in which it is moving is such as to retard the motion.This property of eddy currents is ...

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Radioactive carbon dating:Definition and examples

What is dating? Any of several methods for determining the age of archaeological and fossil remains,rocks,etc,by measuring some property of the organic or inorganic matter that changes with time.This property may be dependent on some aspect of nuclear decay,such as the decay of the radiocarbon or the uranium series ,thermo luminescence ,or electron spin resonance.These aspects are studied by radiometric ...

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Heating effects of electric current and joules law of heating

State Joule’s law of heating “The heat produced in a conductor is: (1) Directly proportion the square of current passing through the conductor,(H ∝ I²) keeping R and t constant; (2) Directly proportion to the resistance of the conductor (H ∝ R) keeping I and t constant;and (3)Directly proportional to the time of flow of current (H ∝ t) keeping I and R ...

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What is difference between excitation and ionization potentials?

Excitation potential: The potential required to lift an electron from ground state to some higher state is called excitation potential. Or If the energy supplied to an electron is such that the electron is lifted from its ground state to one of the higher allowed orbits,the atom will be excited and the energy supplied is called excitation energy or excitation ...

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