Science : Important Laws and Principles in Science

Laws and Principles in Science

Ampere’s Swimming Rule

If we imagine a man is swimming along the wire in the direction of current with his face always turned towards the needle, so that the current enters trough his feet and leaves at his head, then the north pole of magnetic needle will be deflected towards his left hand.

This rule can be recollected with the help of the word snow... snow - current flowing from south to north over magnetic field then deflection of compass or needle is towards west.

Archimedes' principle

Archimedes' principle indicates that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces.

Avogadro’s Law

Equal volumes of all gases under the same conditions of temperature and pressure contain equal number of molecules.

Avogadro's Law is a specific instance of the Ideal Gas Law in which the volume of a gas is directly proportional to the number of moles at constant temperature and pressure.

Black-body Radiation

Black-body radiation is the type of electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, or emitted by a black body held at constant, uniform temperature.

Boyle’s Law

The pressure and volume of a gas have an inverse relationship, when temperature is held constant. We can represent this law by,

P ∝	1
	V

Where, P = Pressure and V = Volume

Charle’s Law

When the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be directly related.

Coulomb’s Law

The magnitude of the electrostatic force of interaction between two point charges is directly proportional to the scalar multiplication of the magnitudes of charges and inversely proportional to the square of the distance between them.

In other language electrostatic force between two point charges reduces to 1/4th of its former value when the distance between them is doubled.

Dalton’s Law

Dalton's law states that the total pressure exerted by the mixture of non-reactive gases is equal to the sum of the partial pressures of individual gases.

Doppler’s Principle

It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. Compared to the emitted frequency, the received frequency is higher during the approach, identical at the instant of passing by, and lower during the recession.

Faraday’s law of Electrolysis

Faraday's 1st Law of Electrolysis

The mass of a substance altered at an electrode during electrolysis is directly proportional to the quantity of electricity transferred at that electrode. Quantity of electricity refers to the quantity of electrical charge, typically measured in coulomb.

Faraday's 2nd Law of Electrolysis

For a given quantity of D.C electricity (electric charge), the mass of an elemental material altered at an electrode is directly proportional to the element's equivalent weight. The equivalent weight of a substance will be explained in the next paragraph.

Fleming's Left hand Rule and Fleming's Right hand rule

When current flows in a wire, and an external magnetic field is applied across that flow, the wire experiences a force perpendicular both to that field and to the direction of the current flow. A left hand can be held, as shown in the illustration, so as to represent three mutually orthogonal axes on the thumb, first finger and middle finger. Each finger is then assigned to a quantity (mechanical force, magnetic field and electric current). The right and left hand are used for generators and motors respectively.

In an electric motor, the electric current and magnet field exist (which are the causes), and they lead to the force that creates the motion (which is the effect), and so the left hand rule is used. In an electric generator, the motion and magnetic field exist (causes), and they lead to the creation of the electric current (effect), and so the right hand rule is used.

Heisenberg’s Uncertainty Principle

Velocity and position of an electron in the orbit of an atom cannot be determined simultaneously.
In other terms we can say that more precisely the position of some particle is determined, the less precisely its momentum can be known, and vice versa.

Ideal Gas Law

The ideal gas law is the equation of state of a hypothetical ideal gas. It is a good approximation to the behavior of many gases under many conditions, although it has several limitations. It was first stated as a combination of Boyle's law and Charles' law. The ideal gas law is often introduced in its common form:

Where,

P = pressure of the gas,
V = volume of the gas,
n = amount of substance of gas (measured in moles),
R = ideal, or universal, gas constant,
T = absolute temperature of the gas.

Inverse Square Law

An inverse-square law is any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity.

Conservation of Mass

The Law of Conservation of Mass states that matter can be changed from one form into another, but the total amount of mass remains constant. We can state this important law in another way. The total mass of the universe is constant within measurable limits; whenever matter undergoes a change, the total mass of the products of the change is, within measurable limits, the same as the total mass of the reactants.

Four Laws of Thermodynamics

Zeroth law of thermodynamics

If two bodies are in thermal equilibrium with a third body then the first two bodies are in thermal equilibrium with each other.

First law of thermodynamics, Conservation of energy, law of conservation of energy

It states that the total energy of an isolated system cannot change—it is said to be conserved over time. Energy can be neither created nor destroyed, but can change form, for instance a car engine burns fuel, converting the fuel's chemical energy into mechanical energy to make the car move.  Windmills change the wind's energy into mechanical energy to turn turbines, which then produce electricity.  Solar cells change sunlight (radiant energy) into electrical energy.

Second law of thermodynamics

This Law states that Mechanical work can be derived from a body only when that body interacts with another at a lower temperature; any spontaneous process results in an increase of entropy.

Third law of thermodynamics

This Law states that the entropy of a substance approaches zero as its temperature approaches absolute zero.

Lenz’s Law

When an emf is generated by a change in magnetic flux, the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it.

Mass Energy Equivalence

In physics, mass–energy equivalence is the concept that the mass of an object or system is a measure of its energy content.

The equivalence of energy E and mass m is reliant on the speed of light c and is described by the famous equation:

Thus, this mass–energy relation states that the universal proportionality factor between equivalent amounts of energy and mass is equal to the speed of light squared.

Newton’s Law of Cooling

Newton's Law of Cooling states that the rate of change of the temperature of an object is proportional to the difference between its own temperature and the ambient temperature (i.e. the temperature of its surroundings).

Newton’s Law of Universal Gravitation

Newton's law of universal gravitation states that any two bodies in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. (Separately it was shown that large spherically symmetrical masses attract and are attracted as if all their mass were concentrated at their centers.)

Newton’s Law of Motion

Newton's laws of motion are three physical laws that together laid the foundation for classical mechanics and can be summarized as follows:

First law

When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force.

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. Can be represented as

F = ma

Where,
F= Force,
m = Mass,
a = Acceleration

Third Law

When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.

Ohm’s Law

Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance, one arrives at the usual mathematical equation that describes this relationship:

Where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.

Pascal’s Law

Pascal's law states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container.
Hydraulic machines work on this principle.