## Pages

### PHYSICS DICTIONARY

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z

Calorie
Quantity of energy required to heat one gram of water through 1 oC .

Centripetal force
It is the force which acts perpendicular to direction of linear velocity to keep body in a circular motion. This force changes direction of linear velocity but not its magnitude.

Centrifugal force
If the radial force acting outwards on the agency which makes body to move in a circular path.

(or)

The pseudo force which acts radially outwards on body moving along a circle.

Critical mass
The minimum quantity of fissile material which is capable of sustaining a fission chain is called critical mass.

Centre of gravity
It is the point of a body through which its weight acts.

Cohesion
The force of attraction between molecules of same substances is called as cohesion.

Charles law
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.

Critical temperature
The highest temperature, below which a gas can be liquefied only by increasing the pressure and above which a gas cannot be liquefied howsoever high pressure may be applied.

Critical pressure
The pressure required to liquefy the gas at critical temperature is called critical pressure of gas.

Critical volume
Volume of unit mass of gas at the critical temperature and critical pressure is called critical volume of gas.

Compton Effect
When a photon of energy ‘hν’ collides with the electron, some of the energy is given to this electron. Due to this energy the electron gains kinetic energy and hence the scattered photon will have lower energy or lower frequency or longer wavelength than incident one which is Compton Effect.

Collision
It is the interaction between the bodies for a small time interval due to which the redistribution of momentum takes place.

Conical pendulum
If the bob of a simple pendulum is pulled to a side and whirled to move along a circle in horizontal plane, the string sweeps a cone and this arrangement is called conical pendulum.

Coefficient of Linear expansion
The ratio of increase in length per degree rise of temperature to the original length of solid.

Coefficient of areal expansion
The ratio of increase in area per degree rise of temperature to the original area of solid.

Coefficient of volume expansion
The ratio of increase in volume per degree rise of temperature to the original volume of the solid.

Canonical Ensemble
It is the collection of large number of essentially independent systems having the same temperature ‘T’, Volume ‘V’ and same no. of identical ‘N’.

Configuration space
The configuration of the system of N particles moving freely in space may be represented by position of a single point in 3N dimensional space which is called configuration space of the system.

Causality Law
Effect cannot precede cause. The interval between two events is same in all inertial frames of reference.

Critical magnetic field
Maximum magnetic field which when applied to a super conductor below transition temperature, the superconducting property is destroyed.

Coherence length
It is defined as the maximum distance up to which the states of pair of electrons are correlated to produce superconductivity.

Centripetal acceleration
The acceleration of object in uniform circular motion, which points towards center, is called as centripetal force.

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”.

Cathodic sputtering
The deposition of metal film by sputtering from a cathode by glow discharge method was first observed by groove. The ejection of atoms from cathode surface by impinging of energetic particle ions of noble gases such as Helium, Argon, Neon, Krypton at a reduced pressure under high DC voltage give rise to sputtering phenomenon called as sputtering.

Clipping circuit
Circuit with which the waveform is shaped by removing a portion of applied wave is known as clipping circuit.

Clausius statement of second law of thermodynamics
It is impossible for a self acting machine, to produce no other effect than to convey heat continuously from one body to another at high temperature.

(Or)

It is impossible for any cyclic machine to produce no other effect than to convey heat continuously from one body to another at a higher temperature.

Crystal
Material, in which atoms are situated in a repeating or periodic array over large atomic distances; that is long range order exists, such that upon solidification, the atoms will position themselves in a repetitive three dimensional pattern, in which each atom is bonded to its nearest neighbor atom.

Celsius
It is unit of temperature. On Celsius scale of temperature, the lower fixed point is melting point of pure ice at normal atmospheric pressure. This is called 0 oC. The upper fixed point is the boiling point of pure water which is designated as 100 oC. The gap between the two fixed points is divided into 100 equal parts or degrees.

Crossection
The probability that an event may occur when a single nucleus is exposed to a beam of particles of total flux containing one particle per unit area.

Closed system
System which cannot exchange matter with surroundings but only exchanges energy with surroundings.

Conservative forces
Forces having property in which work done in displacing an object between two points in space is independent of path taken.

Conservation of momentum
When no external forces acts on system, its linear momentum is constant.

Conduction
Mechanism of heat transfer due to vibration amplitudes of molecules and atoms present in solids.

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.

Covalent bond
It is the bond formed by sharing of pairs of valence electrons between like atoms. The bonding is also known as homo polar or electron pair bonding.

Curie
It is the unit used to describe the strength of a radioactive source in terms of number of disintegrations it undergoes in a unit time. It is designated by Ci. One curie equals 3.7 x 1010 disintegrations per second.
It has originated based on rate of decay of a gram of Radium. Experiments have yielded the result that there are about 3.7 x 1010 disintegrates per second per gram of radium. This number is taken as standard and called Curie.

Choke coil
An inductance coil used in alternating current circuits to limit the current without dissipation of power is called a choke coil. Choke consists of a pure copper wire wounded on a rectangular soft iron to minimize eddy currents and hysteresis losses.

Center of mass
It is the point at which whole mass of body is supposed to be confined. It may lie inside or outside the body.

Conservation of angular momentum
When no external torque acts, then angular momentum of rotating system remains conserved.

Critical angle
It is the angle of incidence of ray travelling from denser to rarer medium, for which angle of refraction becomes 90oC.

Canonical ensemble
It is a collection of large number of essentially independent systems having same temperature, volume and number of particles.

Constancy of speed of light
Observers in all un-accelerated reference frames measure the speed of light (in vacuum) from any source as same. The constant is 3 x 108 m/sec. Remarkable property is referred to as constancy of speed of light.

Coulombs law
The electric forces exerted on each other by two point charges separated by a distance are proportional to product of magnitude of two charges and inversely proportional to the square of distance of separation. The forces act along the line joining the two charges.

Capacitance
It is the ability of dielectric material between conductors to store charge, when a difference of potential exists between the conductors.

Cohesion
It is the force of attraction between molecules of same substances.

Cobalt-60
This is a radioactive element formed by bombarding stable isotope of Cobalt i.e. Co59 with neutrons. Cobalt-60 has half life of 5.3 years which decays by emitting beta followed by gamma rays. In 99.87 % decays, the gamma rays are emitted with 1.17 MeV and in other case with 1.33 MeV.

Cold welding
Welding in which fusion of metal is achieved only by applying pressure and no heat.

Crystalline defect
A lattice irregularity having one or more of its dimensions on order of atomic diameter.

Ceramic
A compound of metallic and non-metallic elements, for which the interatomic bonding is predominantly ionic.

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.

Curie temperature
It is the temperature above which a ferromagnetic or ferrimagnetic material becomes paramagnetic.

Clausius Theorem
The sum of quantities of heat transfer during the isothermal change divided by absolute temperature of isothermal in a reversible cycle is zero.