PHYSICS DICTIONARY

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Kilowatt

It is unit of electric power.

Kilowatt hour (KWH)

It is the unit of electrical energy

Kilowatt Hour

The kilowatt hour is a unit of energy equivalent to one kilowatt of power expended for one hour of time. An energy dissipation of 1 KWH represents 3,600,000 Joules.

Kinematics

Branch of mechanics that studies motion of a body or a system of bodies without considering its mass or forces acting on it.

Kinetic Energy

Energy associated with motion is called “kinetic” energy, from the Greek verb “kinein”, mean “to move”.

Kinetic Theory of Gases

They are set of postulates, by which physical properties of gases can be easily explained.

Kirchhoff’s First Law

It states that at any junction of several circuit elements, the sum of currents entering the junction must be equal to sum of currents leaving it.

Kirchhoff’s Second Law

The algebraic sum of charges in potential around any closed resistor loop must be zero.

Kirchoff’s Law (Thermal Radiation)

The ratio of emissive power to the absorption power is same for all bodies at a certain temperature for a certain wavelength and it is equal to emissive power of a perfectly black body at that temperature and wavelength.

Klystron

Device invented at Stanford University in 1937. It is a type of vacuum tube used as an amplifier / oscillator for UHF and microwave signals. A klystron tube makes use of speed controlled streams of electrons that pass through resonating cavity. Electrons in a klystron are accelerated to controlled speed by application of several hundred volts. As electrons leave the heated cathode of tube, they are directed through a narrow gap into resonating chamber, where they are acted upon by RF signal. The electrons bunch together and are directed into one or more additional chambers that are tuned at or near the tubes operating frequency.

Knot

Unit of speed equal to one nautical mile per hour.

Kronig Penny Model

 It is a simplified model for an electron in one dimensional periodic potential.

Kundt’s Law

Optical absorption bands of a solution are displaced toward the red when its refractive index increases because of changes in composition or other causes.

Kundt’s Tube

It is an acoustical apparatus, invented by German Physicist, August Kundt  (1866 ). It is used to find speed of sound in a solid rod or gas.

PHYSICS DICTIONARY - I4

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Ionosphere

It is that part of atmosphere which is ionized by solar radiation.  The region exists at 85km to 600km altitude, and contains plasma.  It influences radiation propagation to distant places on earth.

Irradiation

Process of exposing a substance to radiation beam of selective dose/energy/type is called as irradiation.

Irrational Number

Real number which cannot be written as a simple fraction.

Irreversible Change

The change which cannot be reversed or the change which on reversing the process, magnitudes of ∆Q, ∆U & ∆W are not same as in direct process is called irreversible change.

Irreversible Process

An irreversible process does not involve restriction of adjusting the external conditions by infitesimal quantities. The system need not remain in equilibrium during the process. Irreversible processes are real processes and can be carried out experimentally. All spontaneous transformations which occur in nature are real processes and hence also irreversible.

Isobaric Process

A process taking place at constant pressure.

Isobars

Nuclides of different elements having same number of nucleons are called isobars.

Isochoric Process

A process taking place at constant volume.

Isolated System

The type of system which has no interaction with its surroundings. Neither energy nor matter can be transferred to or from it.

Isomers

Atoms having same atomic number and mass number but differ from one another in their nuclear energy states and exhibit differences in internal structure are called Isomers. These nuclei are distinguished by their different life times.

 

Isospin

Neutrons and Protons are similar in all respects except charge. On this basis, Heisenberg suggested that these particles are just different manifestations of same inherent particle, the nucleon. To describe their quantum state, quantum number used was termed as isotopic spin quantum number by wigner. It is generally named as isospin or T-spin. The isospin is a vector in a three dimensional space called isospin space which has no relation to physical space.    

Isothermal Process

It is a physical change in which temperature remains constant and there is exchange of heat between system and surroundings and Boyle’s law holds good for this process.

Isotones

Nuclides of elements having same number of Neutrons but different number of Protons are called as isotones.

Isotopes

The atoms of an element, which have same atomic number but different mass numbers are called as isotopes. Number of protons inside the nucleus and number of electrons outside the nucleus of such atoms is same but number of neutrons inside the nucleus is different.

Isotopic Abundance

Refers to the existence of fraction of given isotope for a given element in its normal state.

Isotropic Medium

The medium in which measured properties are independent of direction of measurement.

(or)

Substance in which a physical property have identical values in all crystallographic directions.