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### PHYSICS DICTIONARY

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Induction Heating

It is process of heating metals without physical contact, which uses high frequency electricity to heat materials that are electrically conductive. A source of high frequency electricity is used to drive a large alternating current through a coil. The passage of current through this coil generates a very intense and rapidly changing magnetic field in the space within the work coil. The work piece to be heated is placed with inverse alternate magnetic field. The alternating magnetic field induces a current flow in the conductive work piece. Tremendous currents flow in work piece and are called as eddy currents.

Inelastic Collision

Collision in which only momentum is conserved but not kinetic energy; the colliding bodies undergo deformation.

Inertia

It is inherent property of a body which resists undergoing a change in velocity.

Inertial Frame

The frame with respect to which an un-accelerated body appears un-accelerated is called as inertial frame. In other words, frames which are at rest or in uniform translatory motion relative to one another are inertial frames.

(or)

Frame in which Newton’s first law is true.

Inertial Mass

The inertial mass of a body may be defined as the ratio of the inertial force acting on the body to the acceleration acquired.

Infrasonic Waves

Sound waves of frequency lower than audible limit are called infrasonic waves.

Inhomogeneous System

A linear system of equation AX=B is called inhomogeneous if B0.

Instrumental Error

The error is inherently present in the instrument. This error can be eliminated by replacing the instrument with a similar one or by using a different method for the measurement.

Insulation Resistance

Resistance offered by insulation between two electrodes. Unlike linear resistance, insulation resistance depends on many parameters like surface resistivity, purity of insulation, porosity etc.

Insulator

A non –metallic material that has a filled valence band at 0 K and a relatively wide energy band gap. Consequently, the room temperature electrical conductivity is very low, less than about 10-10 Ohm.m-1.

The intensity of radiation at a point is equal to the radiant energy incident per second on unit area of a surface when the surface is held normal to the incident radiation.

Intensity of Sound

It is the amount of energy passing through a square meter every second. It is measured in watts per square meter. The intensity of sound is related to its amplitude. If amplitude doubles, the intensity is four times greater. Increasing intensity of sound increases its loudness.

Intensity (Sound)

Average rate of transfer of energy per unit area, the area being perpendicular to the direction of propagation of sound.

or

Amount of sound energy crossing per second per unit area normal to the direction of sound wave.

Inter Diffusion

Diffusion of atoms of one metal into another metal is called inter diffusion.

Interfacial Defect

Interfacial defects are boundaries that have two dimensions and normally separate regions of material that have different crystal structures and/or crystallographic orientations.

Interference of Light

The change in uniform distribution of light intensity in a medium due to superposition of two light waves of nearly equal amplitudes, but of same frequency travelling in same direction, is called interference of light.

(or)

Formation of maximum intensity at some points and minimum intensity at some other points by two identical light waves travelling in same direction is called interference of light.

Interferometer

An instrument that measures wavelength, minute distances, refracting of lenses, thickness etc by comparison of interference patterns generated by splitting and reuniting of a beam of light passed through a lens.

Intermolecular Force

The term 'intermolecular forces' is used to describe all the forces, both attractive and repulsive, between groups of neutral molecules or atoms. Intermolecular forces are caused by the attractions and repulsions between the charged particles that make up the atoms in molecules. They are separated into two groups; short range and long range forces. Short range forces come into picture when the centers of the molecules are separated by three angstroms (10-8 cm) or less. Short range forces tend to be repulsive, where the long range forces that act outside the three angstroms range are attractive. Long range forces are also known as Vander Waals forces. They are responsible for surface tension, friction, viscosity and differences between actual behavior of gases. Intermolecular forces are responsible for most properties of all the phases.