Showing posts with label convection. Show all posts
Showing posts with label convection. Show all posts

PHYSICS DICTIONARY

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Constant Error

When a physical quantity is measured a number of times using the same instrument, if the error is same in all measurements, then it is called as constant error.


Constant Pressure Gas Thermometer

It is a thermometer in which volume occupied by a given mass of gas at constant pressure is used to determine a temperature.


Constant Volume Gas Thermometer

It has a thin walled glass container and manometer. The glass container is full of gas.


Constantan

An alloy of Copper and Nickel, usually 60% Cu and 40% Ni . The alloy has high resistance and low temp coefficient, hence used in resistance wires and thermocouples.


Constrained Motion of a Rotating Body

If some restrictions are imposed on individual particles of system like restriction to change their positions or velocities, the system is called “constrained system”.


Constructive Interference

Interference at the points where the intensity of light is maximum is called as constructive interference.


Continuous Spectrum

It contains all wavelengths from violet to red. It is given by incandescent (red hot) solids and liquids. It is not the characteristic of an atom or molecule but it is emitted by matter bulk. It depends on temperature of source. It is due to thermal excitation.                                                              

Control Rod

Devices having high absorption cross section for neutrons used in nuclear reactor to control the neutron reactivity , influencing availability of neutrons to cause fission thus effecting criticality of reactor.


Convection

Mechanism of heat transfer through fluids like air or water when comes into contact with an object whose temperature is higher than that of fluid. As temperature of fluid in contact with hot body increases, expands & thus becomes less dense and due to buoyant forces it raises and the position is occupied by cooler surrounding fluid and the process continues.


Converging Lens

See convex lens.


Conversion Electron

See internal conversion.


Convex Lens

It is lens that bulges outward and thicker at center. It is an optical device which converge transmitted light to a focus.


Coolant(Reactor)

Coolant is a fluid having high boiling point and high specific heat, used in nuclear reactor to remove the heat liberated during the fission process in fuel bundles.   


Coolidge X-ray Tube

In 1914 William Coolidge, an American physicist, introduced a new X-ray tube design based on a hot cathode which drastically improved the reliability and performance of clinical X-ray tubes.

The hot cathode consists of a filament made of a high melting point metal, typically Tungsten (melting point 3422 C) or a Tungsten based alloy, heated to a relatively high temperature to serve as source of electrons. The hot cathode emits electrons thermionically. Emitted electrons are accelerated towards target material (anode), from which X-rays are generated.


Cooper Pairs

Cooper showed that an arbitrarily small attraction between electrons in a metal can cause a paired state of electrons to have lower energy than the Fermi energy, which implies that the pair is bound. BCS theory of super conductors took basis of cooper pairs, which are presumed to be formed due to electron– phonon interaction at extremely low temperatures. The coupling is over a range of hundreds of nanometers. They take character of Boson at low temperatures are condense into ground state.


Coordinate Bond

A coordinate bond is a covalent bond between two atoms where one of the atoms provides both electrons that form the bond.


Coordinate Geometry

The use of algebra to study geometric properties; operates on symbols defined in a coordinate system


Coordinates

Coordinates are set of values that show an exact position of a point or object in reference frame.


Co-ordination Number

Number of nearest neighbor atoms for a particular atom at a lattice point is called as coordinate number. In chemistry, it is the number of atoms linked or bonded to a particular atom.  


Coriollis Force

Fictitious force acting on an object in non-inertial frame is known as coriollis force.


Corona Discharge

An electrical discharge characterized by a corona, occurring when one of two conducting surfaces (such as electrodes) of differing voltages has a pointed shape, resulting in a highly concentrated electric field at its tip that ionizes the air (or other gas) around it. Corona discharge can result in power loss in the transmission of electric power, and is used in photocopying machines and air-purification devices. 

Heat Transfer due to convection

In this type of heat transfer, molecules of fluids move up bodily due to heating. Such heat transfer occurs when a fluid such as air or water comes in contact with an object whose temperature is higher than that of fluid. As temperature of fluid in contact with hot body increases, the fluid expands and thus becomes less denser and due to buoyant forces it rises & the position is occupied by cooler surrounding fluid and the process continues.

"Convection" is part of many natural process. Atmospheric convection plays an important role in determining global climate patterns & daily weather changes.

The rate of heat transfer by convection depends on the temperature difference between the surfaces and also on their areas.