Theories-Laws-Principles
Discover an in-depth exploration of Scientific Theories-Laws-Principles, covering their definitions, key examples, and the differences between them, to better understand how they shape our understanding of the natural world.
Theories-Laws-Principles
1. Laws of Heredity
- The principles of inheritance are termed Mendel's theory. The laws of heredity are-
(i) Law of segregation
(ii) Law of Independence Assortment
(iii) Law of Paired Factors
(iv) Law of Dominance
2. Lamarck theory
- The theory states that the effective and ineffective use of organs bring some changes in the structure of living bodies.
3. Archimedes Principle
-When an object is (Wholly or partially) immersed in a liquid, it experiences a buoyant force (upthrust) which is equal to the weight of the liquid displayed by the object.
Buoyant force for (upthrust)= weight of the liquid displaced by that object.
Avograde’s Law:
Equal volumes of all gases under the same conditions of temperature and pressure contain an equal number of molecules.
4. Boyle’s Law: At constant temperature, the volume of a given mass of gas varies inversely to its pressure.
5. Charle’s Law: At constant pressure, the volume of a given mass of gas is directly proportional to its absolute temperature.
6. Coloumb’s law: When the distance between the two electric charges gets doubled, the force between them reduces to a quarter of its former value.
7. Dalton’s Law: When two or more gases that do not react chemically with one another, are enclosed in a vessel, then the total pressure exerted by the mixture of gases will be equal to the sum of partial pressures that each gas would exert, if present alone in that space.
8. Ohm’s Laws: At constant temperature, a current flowing through a conductor of a uniform area of cross-section is proportional to the difference of the potential across its terminals.
Pascal’s law: The pressure, applied any wherein a mass of confined incompressible fluid (or liquid), is transmitted by the fluid in all directions and acts undiminished at every point of the fluid and at right angles to the surface exposed to the fluid.
9. Faraday’s Law of Electrolysis:-First Law: The mass of the substance liberated at the electrode as a result of electrolysis is directly proportional to the quantity of electricity passed through the electrolyte.
-Second Law: When the same quantity of electricity is passed through different electrolytes connected in series, then the mass of the different substances liberated at the electrodes is proportional to their equivalent masses.
10. Uncertainty Principle- It is impossible to measure simultaneously both the position and velocity (or momentum) of a microscopic particle with absolute accuracy or certainty.
11. Inverse-square Law- The force of attraction between two unlike magnetic poles and the force of repulsion between two like poles are proportional to the square of the distance between them. This law is true for electric charges too.
12. Graham’s law of diffusion: -Under similar conditions of temperature and pressure, the rates of diffusion of gases are inversely proportional to the square root of their densities.
13. Law of conservation of matter: Matter is neither created nor destroyed in chemical charges. The sum total of the masses of all the products of a chemical change is exactly equal to the sum total of the substances from which these products have been formed.
14. Mass-Energy Equation: E= mc2 ; which implies that mass and energy are interchangeable, Where E=quantity of energy released from the annihilation of matter of mass ‘m’. Velocity of light.
15. Newton’s Universal Law of Gravitation
Every particle of matter in this universe attracts each other with a force that varies directly as the product of masses of two particles and inversely as the square of the distance between them.
16. Newton’s Law of Motion :
-First Law: It states that a body continues its state of rest or uniform motion in a straight line unless a force is applied to it to change the state of the body.
-Second law: The rate of change of momentum of a moving body is proportional to the applied force and takes place in the direction of the force.
-Third Law: Whenever one body exerts a force on another body, the second body exerts an equal and opposite force on the first body.
17. Newton’s Law of Cooling-The rate at which a body cools or loses its heat to its surroundings is proportional to the excess of the mean temperature of the body over that of the surroundings provided this temperature excess is not too large.
18. Laws of Refraction:
-The sine of the angle of incidence bears a constant ratio with the sense of the angle of refraction, i.e. = constant.
-The incident ray, the refracted ray and the normal to the interface at the points of incidence all lie in one plane and that plane is perpendicular to the interface separating the two media.
Laws of natural selection:
-It stressed the point that living beings struggle for their existence.
19. The basis of Darwin’s theory is-
(i) High rate of reproduction
(ii) Struggle for existence
(iII) Survival of the fittest
(iv) Natural selection.
20. Laws of Reflection
-The incident ray, the reflected ray and the normal to the reflecting surface at the point of incidence, all lie in one plane and that plane is perpendicular to the reflecting surface.
-The angle of incidence is equal to the angle of reflection, i.e. i= r
Modern Periodic Law
- It states that “the physical and chemical properties of the elements vary periodically as their atomic numbers”.
Common Numerical Values
Ï€= 3.1416 (22/7)
Lower fixed point of Celsius Scale = 00C
Upper fixed point of Celsius scale = 1000C
Lower fixed point of Fahrenheit scale = 320F
Upper fixed point of Fahrenheit scale = 2120C
Velocity of light= 3X108 m/s
Magnitude of universal gravitational constant = 6.67X10-11 Nm2/kg2
Acceleration due to gravity on the surface of the earth = 9.8 m/s2
Mass of the earth = 6X1024 kg
The average radius of the earth = 6.4X106m
1 H.P. = 746 watt= 0.746 kilowatt
1 calorie = 4.186 Joule
Specific heat of water = 4.18x103 J/ kg/0C
Specific heat of ice = 2.14x103 J/ kg/0C
Latent heat of fusion of ice = 80 cal/gm=336X103 J/ kg
Latent heat of vapourisation of water = 540 cal/gm=2268X103 J/ kg
1 Light year = 9.4607x1012 km
1 Parsec = 3.26 Ly
Astronomical unit (AU) = 1.496 X 108 km
Astronomical Year = 225 X 106 km
Diameter of the sun = 1.39 X 106 km
Distance of earth from the sun = 150 X 106 km
Distance of the moon from the earth = 3.84 X 105 km
Escape velocity = 11.2 km/s
Mass of a hydrogen atom = 1.67 X10-27 kg
1 atmospheric pressure ( 1 atmm)
= 1.01325X 105 N/m2
=1.01325 x 105 Pascal
At N.T.P., the gram molecule volume of a gas = 22.4 liters.
Avogrdro’s number = 6.00221 x 1023 per mole.
Magic numbers: 2, 8, 8, 18 and 32 numbers
Number of periods in Modern Periodic Table = 7
Number of groups in Modern Periodic Table = 18
1 Angstrom (A0) = 10-8 cm= 10-10 m
Important Formulae Used in Science
Area of a Rectangle = Length X Breadth
Area of a Square = (Length of a side)2
Area of a triangle = 1/2 X base X altitude
Area of a Circle = πr2 ( r is the radius of the circle)
Circumference of a Circle = 2Ï€r
The surface area of a Rectangular Parallelopiped (A)= 2(lb+bh+hl)
Where, l=length, b=breadth and h=height
Surface area of a cube (A)= 6l2, Where, l=length of side
Surface area of a cylinder, A= 2Ï€r (r+h) , Where, r= radius of the base, h=height
Surface area of a sphere, A=4Ï€r2
Volume of a Cylinder, V=Ï€r2h
Volume of a sphere =4/3Ï€r3
Density, d= m/v, where, m=mass, v=volume
Speed or velocity =s/t, where s=distance, t=time
Average Speed= Total distance /Total time taken
Average Velocity =(Initial velocity + Final velocity)/2
v=u+at, where v=final velocity, u=initial velocity, a=acceleration, t=time.
s=ut + 1/2 at2 where, s=distance
v2=u2+ 2as
Applied unbalanced Force = mass X acceleration or, F=ma
Momentum= mass x velocity or, P=mv
F= G. m1m2/R2 v2= u2+ 2gh , Where, v= final velocity, u=initial velocity, g=acceleration due to gravity, t=time, h=height
(ii) For bodies moving vertically upwards against gravity:
V= u-gt
h=ut-1/2gt2
v2=u2-2gh
Work= Force X displacement in the direction of force or, W=F X d
Work done in vertical displacement:
W=mgh
where, m=mass of the body, g=acceleration due to gravity, h=height
Power= Work done/Time taken or, P= W/t
Kinetic Energy, Ek= 1/2 mv2 Potential Energy, Ep= mgh
Power = Energy supplied/Time Or, P=E/t
Boyle’s Law: PV= Constant (mass and temperature remaining constant) where, P=pressure of gas, v=volume of gas.
Charle’s Law: V/T= Constant (mass and pressure remaining constant) where V=volume of gas; T=absolute temperature of gas.
Gas Equation: PV/T= Constant (mass remaining constant)
Pressure (P) = F/a, where, F=normal force, a=surface area
Relation between Celsius and Fahrenheit scales of Temperature: C/5= (F-32)/9
Where, C=temperature in Celsius scale; F=temperature in Fahrenheit scale
Heat gained or Heat lost, H=mst
Where m= mass of the body
s=specific heat,
t= change in temperature
Principle of Calorimetry
Heat lost =Heat gained
Relative humidity = (Vapour pressure of air t0C/Saturated vapor pressure at t0C) X 100%.
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