WELCOME TO

KAMESHPOWERPOINT

LAW OF

CONSERVATION OF

ENERGY

Law:In physics, the law of conservation of energy states that the total energy of an isolated system remains

constant—it is said to be conserved over time. Energy can be neither created nor be destroyed, but it

transforms from one form to another, for instance chemical energy can be converted to kinetic energy in

the explosion of a stick of dynamite.

HISTORYAncient philosophers as far back as Thales of Miletus c. 550 BCE had inklings of the

conservation of some underlying substance of which everything is made. However, there is no particular reason to identify this with what we know today as "mass-energy" (for

example, Thales thought it was water). Empedocles (490–430 BCE) wrote that in his universal system, composed of four roots (earth, air, water, fire), "nothing comes to be

or perishes";[2] instead, these elements suffer continual rearrangement.In 1638, Galileo published his analysis of several situations—including the celebrated

"interrupted pendulum"—which can be described (in modern language) as conservatively converting potential energy to kinetic energy and back again.

It was Gottfried Wilhelm Leibniz during 1676–1689 who first attempted a mathematical formulation of the kind of energy which is connected with motion (kinetic energy). Leibniz noticed that in many mechanical systems (of several masses, mi each with

velocity vi )

A key stage in the development of the modern conservation principle was the demonstration of the 

mechanical equivalent of heat.The caloric theory maintained that heat could neither be

created nor destroyed, whereas conservation of energy entails the

contrary principle that heat and mechanical work are interchangeable

In the middle of the eighteenth century Mikhail Lomonosov, a Russian scientist, postulated his corpusculo-kinetic theory of heat, which rejected the idea of a caloric. Through the results of empirical studies, Lomonosov came to the

conclusion that heat was not transferred through the particles of the caloric fluid

Mechanical equivalent of heat

Meanwhile, in 1843 James Prescott Joule independently discovered the mechanical equivalent in a series of

experiments. In the most famous, now called the "Joule apparatus", a descending weight attached to a string

caused a paddle immersed in water to rotate. He showed that the gravitationalpotential energy lost by the weight in descending was equal to the internal energy gained by the

water through friction with the paddle.

It continues………………

Matter is composed of such things as atoms, electrons, neutrons, and protons. It has intrinsic or rest mass. In

the limited range of recognized experience of the nineteenth century it was found that such rest mass is conserved. Einstein's 1905 theory of special relativity

 showed that it corresponds to an equivalent amount of rest energy. This means that it can be converted to or from equivalent amounts of other (non-material) forms

of energy, for example kinetic energy, potential energy, and electromagnetic radiant energy. When this

happens, as recognized in twentieth century experience, rest mass is not conserved, unlike the total mass or totalenergy. All forms of energy contribute to

the total mass and total energy.

Mass–energy equivalence

Conservation of energy in beta decayThe discovery in 1911 that electrons emitted in beta decay have

a continuous rather than a discrete spectrum appeared to contradict conservation of energy, under the then-current

assumption that beta decay is the simple emission of an electron from a nucleus. This problem was eventually resolved in 1933

by Enrico Fermi who proposed the correct description of beta-decay as the emission of both an electron

and an antineutrino, which carries away the apparently missing energy.

Noether's theorem

The conservation of energy is a common feature in many physical theories. From a mathematical point of view it is

understood as a consequence of Noether's theorem, developed by Emmy Noether in 1915 and first published in 1918. The theorem states every continuous symmetry of a

physical theory has an associated conserved quantity; if the theory's symmetry is time invariance then the conserved

quantity is called "energy". The energy conservation law is a consequence of the shift symmetry of time; energy

conservation is implied by the empirical fact that the laws of physics do not change with time itself

Quantum theoryIn quantum mechanics, energy of a quantum system is described by a self-adjoint (or

Hermitian) operator called the Hamiltonian, which acts on the Hilbert space (or a space of wave functions ) of the system. If the Hamiltonian is a time independent operator, emergence probability of the measurement result does not change in time over the

evolution of the system. Thus the expectation value of energy is also time independent. The local energy conservation in quantum field theory is ensured by the quantum

Noether's theorem for energy-momentum tensor operator. Note that due to the lack of the (universal) time operator in quantum theory, the uncertainty relations for time and

energy are not fundamental in contrast to the position-momentum uncertainty principle, and merely holds in specific cases (see Uncertainty principle). Energy at each

fixed time can in principle be exactly measured without any trade-off in precision forced by the time-energy uncertainty relations. Thus the conservation of energy in

time is a well defined concept even in quantum mechanics.

Law of Conservation of Energy

• What you put in is what you get out

• Total energy is conserved

Practical Applications

• Gasoline converts to energy which moves the car

• A battery converts stored chemical energy to electrical energy

• Dams convert the kinetic energy of falling water into electrical energy

Can You Think of Other Examples?

Conservation of Mechanical Energy

Emghmv 221

Total Energy

Potential Energy

Kinetic Energy

m = mass

v = velocity

g = gravitational acceleration

h = height

ILYA, did you know that

even though it was a bumpy

ride, our energy

remained constant!

Example of Conservation of Mechanical Energy

Emghmv 221

Constant

An Example

Another Example

Yet Another Example

THANK YOU FRIENDS