## Important Scientific Laws and Theories

Archimede's principle:
It states that a body when wholly or partially immersed in a liquid, experiences an upwa rd thrust which is equal to the weight of the liquid displaced by it. Thus, the body appears to lose a part of its weight. This loss in weight is equal to the weight of the liquid displaced by the body.
Aufbau principle
It states that in an unexcited atom, electrons reside in the lowest energy orbitals available to them.
It states that equal volumes of all gases under similar conditions of temperature and pressure contain equal number of molecules.
Brownian motion
It is a zi gzag, irregular motion exhibited by small solid particles when suspended in a liquid or gas due to irregular bombardment by the liquid or gas molecules
Bernoulli's principle
It states that as the speed of a moving fluid, liquid or gas, increases, the pressure within the fluid decreases. The aerodynamic lift on the wing of an aeroplane is also explained in part by this principle.
Boyles's Law
It states that temperature remaining constant, volume of a given mass of a gas varies inversely with the pressure of the gas. Thus, PV = K (constant), where, P = Pressure and V = Volume.
Charles's Law
It states that pressure remaining constant, the volume of a given mass of gas increases or decreases by 1/273 part of its volume at 0 degree celsius for each degree celsius rise or fall of its temperature.
Coulomb's Law
It states that force of attraction or repulsion between two charges is propor tional to the amount of charge on both charges and inversely proportional to the square of the distance between them.
Heisenberg principle (uncertainty principle) -
It is impossible to determine with accuracy both the position and the momentum of a par ticle such as electron simultaneously
Gay - Lussac’s Law of combining volumes
Gases react together in volumes which bear simple whole number ratios to one another and also to the volumes of the products, if gaseous — all the volumes being measured un der similar conditions of temperature and pressure.
Graham’s Law of Diffusion
t states that the rates of diffusion of gases are inversely proportional to the square roots of their densities under similar conditions of temperature and pressure.
Kepler's Law
Each planet revolves round the Sun in an elliptical orbit with the Sun at one focus. The straight line joining the Sun and the planet sweeps out equal areas in equal intervals. The squares of the orbital periods of planets are proportiona l to the cubes of their mean distance from the Sun.
Law of Floatation
For a body to float, the following conditions must be fulfilled:
1. The weight of the body should be equal to the weight of the water displaced.
2. The centre of gravity of the body and that of the liquid displaced should be in the same straight line.
14. Law of conservation of energy
It states that energy can neither be created nor destroyed but it can be transformed from one form to another. Since energy cannot be created o r destroyed, the amount of energy present in the universe is always remain constant.
Newton's First Law of Motion
An object at rest tends to stay at rest, and an object in motion tends to stay in motion, with the same direction and speed in a straigh t line unless acted upon by some external force.
Newton's Second Law of Motion
The rate of change of momentum of a body is directly proportional to the force applied and takes place in the direction in which the force acts.
Newton's Third Law of Motion
To every action there is an equal and opposite reaction
Newton's Law of Gravitation
All particles of matter mutually attract each other by a force directly proportional to the product of their masses and inversely proportional to the sq uare of the distance between them.
Ohm's Law
t states that the current passing through a conductor between two points is directly proportional to the potential difference across the two points provided the physical state and temperature etc. of the conductor does not change.
Pauli exclusion principle
It explains that no two electrons in the same atom or molecule can have the same set of quantum numbers.