## Pages

### PHYSICS DICTIONARY

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Gravitational potential
Gravitational potential at a point in gravitational field is amount of work done in bringing a unit mass from infinity to that point.

Geo-stationary satellite
A satellite which appears to be stationary relative to earth is called geo stationary satellite. The direction of motion and magnitude of orbital velocity of satellite are same as that of earth. Satellite revolves from west to east in equatorial plane.

Grand Canonical Ensemble
It is collection of large number of essentially independent systems having same temperature, volume and chemical potential.

Gauss’s theorem of magnetism
The total magnetic flux through any closed surface is always zero.

Gauss’s theorem of electrostatics
The net outward electric flux through any closed surface of any shape in an electric field is equal to
1/εo times the total charge contained within that surface.

Gauge pressure
When pressure is measured either above or below atmospheric pressure as a arbitrary datum then it is called gauge pressure.

Gamma rays
Electromagnetic radiation emitted from nucleus as a result of transition of nucleons between energy states inside nucleus (or) electromagnetic radiation emitted in annihilation reaction between matter and antimatter.

Gravitational Intensity
Gravitational force of attraction exerted by a body on unit mass is called gravitational intensity.

Gray
It is the SI unit for Radiation Absorbed Dose(RAD) which is equal to absorption of 1 Joule per Kg of material.

Grain boundary
It is defined as boundary separating two small grains or crystals having different crystallographic orientations in poly crystalline materials.

Gas
The gaseous state above critical temperature of substance is called as gas.

Gravitational force
It is the force of attraction between any two objects in the universe. It is a long range and central force.

Geocentric theory
Theory proposed by Ptolemy, as per which all the planets and the sun revolve round the earth.

Gravitational potential
Gravitational potential at a point in the gravitational field is the amount of work done in bringing a unit mass from infinity to that point.

Geo-stationary satellite
A satellite which appears to be stationary relative to the earth is called as geo stationary satellite. The time period of revolution of a parking satellite is 24 hours. Height of the geo-stationary orbit above the surface of earth is about 36000KM.

Gravitational mass
The ratio of gravitational force acting on a body to the acceleration due to gravity is called as gravitational mass.

Grand canonical ensemble
It is the collection of large number of essentially independent systems having same temperature ‘T’, volume ‘V’ and chemical potential ‘µ’. The individual systems of a grand canonical ensemble are separated by rigid permeable and conducting walls.

Gyroscope
If the fixed point, about which a symmetrical body is spinning about its axis, coincides with center of gravity of body, then it is known as gyroscope. The device consists of rotation, precession and nutation.

Gyration
Simultaneous precession, nutation & rotation of body is called gyration of the body.

Gauge pressure
When pressure is measured either above or below atmospheric pressure as a arbitrary datum then it is called as gauge pressure.

Geiger-Nuttal law
This law implies an empirical relation between range of an alpha particle ‘R’ and decay constant ‘λ’ of alpha emitter as

Log R = A Log λ + B

Where ‘A’ is a constant having same value for all three radioactive series and ‘B’ is constant different for each series. This law has acquired prominence in nuclear physics because it enabled physicists to estimate half lives of alpha emitters which couldn’t be easily determined by experimental results.