Showing posts with label charge. Show all posts
Showing posts with label charge. Show all posts

PHYSICS DICTIONARY

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Cerenkov Radiation

Electromagnetic radiation emitted when a charged particle passes through a dielectric medium at a speed greater than phase velocity of light in that medium. The charged particles polarize the molecules of that medium, which then turn back rapidly to their ground state emitting radiation in the process.  For instance, speed of light in water is 0.75C. Matter can be accelerated beyond this speed during nuclear reactions and in particle accelerators.


Cermet

A composite material, consisting of a combination of ceramic and metallic materials is called as ceramic. The most common cermets are the cemented carbides, compound of an extremely hard ceramic, bonded together by a ductile metal such as Cobalt or Nickel. 


CGS Units

Acronym for Centimeter – Gram – Second system is a metric system of physical units based on centimeter as unit of length, gram as a unit of mass, and second as a unit of time.


Chain Reaction

Process of multiplicity of neutrons in nuclear reactor to sustain nuclear fission is called as chain reaction. It was proposed by Leo Szilard in 1933.


Chandrasekhar Limit

It was proposed by Chandrasekhar that no white dwarf star can have mass larger than 1.4 times mass of sun.


Characteristic X-ray Radiation

The production of "characteristic" X-rays by electron bombardment of pure elements was first observed in 1909 by Charles G. Barkla and C.A. Sadler. When heavy metals are bombarded with energetic particles, electrons may get knocked out. If the electrons are knocked out from the inner shells of atom, the vacancy is filled by the transition of electrons from outer shells. This will result in emission of quantized photons, "characteristic" of the element.


Charge Conjugation

It is defined as interchange of particles and antiparticles. It doesn’t simply mean a change over the opposite electric charge or magnetic moment, but the sign of certain charge quantum numbers also change. 


Charge Coupled Device

It is a light sensitive integrated circuit that stores and displays the data for an image in such a way that each pixel in the image is converted into an electrical charge, the intensity of which is related to color in the color spectrum.


Charge Transfer Device

A charge-transfer device has a metal oxide semiconductor (MOS) structure that is composed of many independent pixels where charge is stored in such a way that the charge pattern corresponds to the irradiation pattern. These devices can be linear or two-dimensional. According to the method used to detect the charge pattern, two types of charge-transfer devices can be distinguished: charge-coupled devices (CCDs) and charge-injection devices (CIDs).


Charge

It is characteristic of an object that expresses the extent to which it has excess or deficiency of electrons. If the object has deficiency of electrons, then it is said to be having negative charge. In fact it is technical term used to indicate that an object has been prepared to participate in electrical forces.


Charles law

At constant pressure, the volume of a given mass of gas is directly proportional to its absolute temperature.

(or)

At constant pressure, volume of a given mass of a gas increases (or decreases) by (1/273)th part of its volume at 0 oC, on increasing (or decreasing) the temperature by 1oC.


Chemiluminescence

Phenomenon of emission of electromagnetic radiation as light by the release of energy from a chemical reaction is called as chemiluminescence.


Chemisorption

If the adsorbate molecules are bound to the surface of adsorbent by chemical bonds, the adsorption is known as chemical adsorption or chemisorption.


Cherenkov Radiation

When a high energy charged particle with non – zero rest mass, such as an electron, travels faster than speed of light in a medium, then it emits a special kind of radiation called Cherenkov radiation. The wavelength of Cherenkov photons falls in and around visible region of EM spectrum. In fact, first Cherenkov radiation was observed by Pavel Cherenkov in 1934 as blue light coming from a bottle of water undergoing bombardment by particles from a radioactive source.


Chi-square Distribution

It is one of the most widely used probability distribution  in  inferential statistics, e.g., in hypothesis testing or in construction of confidence intervals. The Chi-Square distribution is merely the distribution of the sum of the squares of a set of normally distributed random variables. Its value stems from the fact that the sum of random variables from any distribution can be closely approximated by a normal distribution as the sum includes a greater number of samples. Thus the test is widely applicable for all distributions. 

Difference between Charge, Voltage & Currrent



Electrical Charge

Electrical charge is a fundamental quantity and is intrinsic property of matter which causes a force to act between particles (objects, bodies..) which have this property. It is physical quantity which can be transferred from one object to another.

Electric charge comes in two types, which wechoose to call positive charge and negative charge.

Electric charge can be measured using the law for the forces between charges (Coulomb’s Law). Charge is a scalar and is measured in coulombs. The coulomb is actually defined in terms of electric current (the flow of electrons), which is measured in amperes; when the current in a wire is 1 ampere, the amount of charge that flows past a given point in the wire in 1 second is 1 coulomb. Thus,

 
when charges are transferred by simple interactions (i.e. rubbing), it is a negative charge which is transferred, and this charge is in the form of the fundamental particles called electrons. The charge of an electron(e) is -1.6022 × 10-19 C.


The particles found in nature all have charges which are integral multiples of the elementary charge e:
 q = ne where n = 0, ±1, ±2 . . .. Because of this, we say that charge is quantized.


A charged object is an object that has an excess of one type of charge, e.g., more positive than negative. The amount of excess charge is the charge we assign to that object.
 
Current

Flow of charge moving through unit area in unit time. It represents charge transfer.


Voltage/Potential Difference

Voltage is a measure of the energy carried by the current. Technically it is a measure of the difference in energy between two points – hence the name potential difference. Voltage represents potential difference between two points. It represents work to be done to move unit charge from one point to other under influence of electric field.