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### PHYSICS DICTIONARY

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Kilogram
The Kilogram is the usual scientific unit of mass. The standard Kilogram is the mass of a particular cylinder of platinum iridium alloy kept near Paris in France. All masses that are measured are compared with this.

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.

Kelvin’s Thermodynamic Scale
The ratio of two temperatures measured on absolute scale is equal to the ratio of heat absorbed to the heat rejected by a reversible engine working between these temperatures.

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 that wavelength.

Kilowatt hour (KWH)
It is the unit of electrical energy. 1KWH=36 x 105 Joules.

Kepler’s first law
Every planet revolves round the sun in an elliptical orbit with the sun at one of its foci. This law is known as law of orbits.

Kepler’s second law
The radius vector joining a planet to the sun sweeps equal areas in equal intervals of time.
(or)
The areal velocity of a planet round the sun is constant. This law is known as “law of areas”.

Kepler’s third law
Square of the time period of revolution of a planet round the sun is directly proportional to the cube of mean distance of the planet from the sun.

Kelvin’s statement of second law of thermodynamics
It is impossible to get a continuous supply of work by cooling a body to a temperature lower than that of coldest of its surroundings.

Kilo Calorie
The amount of energy required top increase the temperature of one kilogram of water by 1oC.