E E == mc mc22

E = mcE = mc22 is everywhere! is everywhere!

E E == mc mc22

Energy (in Energy (in joulesjoules))

= Mass (in = Mass (in kilogramskilograms) ) XXThe Speed of Light SquaredThe Speed of Light Squared(in (in meters squared per second meters squared per second

squaredsquared) )

The big question???The big question???

How much How much energy will energy will one liter of one liter of

water yield if water yield if it is it is

converted converted entirely into entirely into

energy?energy?

But Chemistry says matter But Chemistry says matter cannot be created nor be cannot be created nor be

destroyed???destroyed???

No it’s Not!

Matter and Energy are two forms of the same

thing!

Neither can be destroyed but, under

special circumstances, either can be turned

into the other

Lots of energy goes into making even a

small mass and it can also be got back in

some form.

E = mc2 tells you exactly how much

energy a given amount of mass

contains.

The speed of light…The speed of light…

Light travels three hundred million Light travels three hundred million meters in a second i.e. 300,000,000 meters in a second i.e. 300,000,000 m/sm/s

So So (forgetting the units for now)(forgetting the units for now)

Energy = mass x (300,000,000)Energy = mass x (300,000,000)22

or E = m or E = m (90,000,000,000,000,000)(90,000,000,000,000,000)

= m (9 x 10= m (9 x 101616))..

That’s aBIGlot

MassMass

What is the mass of 1 liter of water?What is the mass of 1 liter of water?A liter of water is defined to have a A liter of water is defined to have a

mass ofmass of one kilogram!one kilogram!

m = 1m = 1

So, E = 1 (9 X 10So, E = 1 (9 X 101616)) = 9 X 10= 9 X 101616 Joules Joules

What could we do with all this

energy?

Energy & PowerEnergy & PowerA Joule is the effort required to push A Joule is the effort required to push

one kilogram over a meter at an one kilogram over a meter at an acceleration of one meter/secondacceleration of one meter/second22..

A Joule expended continuously for one A Joule expended continuously for one second is a Watt.second is a Watt.A liter of water, converted to energyA liter of water, converted to energy

could power a 1 watt light bulb for…could power a 1 watt light bulb for…

9x109x101616 seconds, or 2.5x10 seconds, or 2.5x101313 hours hours

or ~3 billion years! (2/3 the age of the or ~3 billion years! (2/3 the age of the Earth)Earth)

A 100 Watt bulb…A 100 Watt bulb…would only stay lit for 2.5 x 10would only stay lit for 2.5 x 101111 hours! hours!

There are about 10There are about 1099 families on families on EarthEarth

So let’s light 10So let’s light 109 9 bulbs of 100 Watt bulbs of 100 Watt powerpower

for for 250250 hours…!hours…!

YouYouspend the same amount of energyspend the same amount of energy

as a 100 watt bulb !as a 100 watt bulb ![ One joule is equal to about four food [ One joule is equal to about four food

calories]calories]

The downsideThe downside

200,000 people have been killed by just 2 atomic bombs.

One Hydrogen Bomb could kill 50 times as many!

Most environment friendly Most environment friendly applicationapplication

All our energy All our energy comes from comes from the Sun!the Sun!

The Sun has The Sun has E=mcE=mc22 as its as its source of source of energyenergy..

Nuclear FusionNuclear Fusion

When When 4 hydrogen 4 hydrogen nucleinuclei are fused are fused together into together into 1 1 helium nucleushelium nucleus, , energy is released energy is released in the form of in the form of Light photonsLight photons and particles and particles called called neutrinosneutrinos..  

But where does the mass But where does the mass come from?come from?

Mass of 4 hydrogen nuclei is Mass of 4 hydrogen nuclei is moremore than that of 1 helium nucleusthan that of 1 helium nucleus

So after fusion a little bit of mass is So after fusion a little bit of mass is left over. This mass deficit appears left over. This mass deficit appears as the energy of light and as the energy of light and neutrinosneutrinos..

A look inside the sunA look inside the sun

The fusion happens 700,000 km deep in the Sun’s core.

It requires a temperatures of 15 million oC.

Solar E = mcSolar E = mc22

How much mass does it How much mass does it convert each second in convert each second in order to shine?order to shine?

If the Lifetime of the SunIf the Lifetime of the Sun

is 10is 101010 years, how years, how much mass would it much mass would it need in that time?need in that time?

Use Use m = E/cm = E/c2 2 !!

The Sun emits 4 x 1026 joules per second

How do you convert any mass How do you convert any mass to Energy on Earth?to Energy on Earth?

Scientists are trying to make a sun Scientists are trying to make a sun on the Earth through fusion on the Earth through fusion reactors that use hydrogen.reactors that use hydrogen.

Hydrogen is the simplest & lightest Hydrogen is the simplest & lightest element.element.

Hydrogen is abundantly found in water!Hydrogen is abundantly found in water!

Hydrogen fusion has been tried and Hydrogen fusion has been tried and tested in Nature and on Earth (in H-tested in Nature and on Earth (in H-Bombs).Bombs).

The only scientist that was The only scientist that was able to accomplish sustained able to accomplish sustained

nuclear fusion..nuclear fusion..

What are the barriers to What are the barriers to attaining nuclear fusion?attaining nuclear fusion?

Hydrogen is a diffused gas and it is Hydrogen is a diffused gas and it is difficult to get its nuclei close enough difficult to get its nuclei close enough to fuse.to fuse.

They start colliding into each other only They start colliding into each other only at a temperature of 15 million degrees at a temperature of 15 million degrees C.C.

We need to keep it both hot & dense.We need to keep it both hot & dense.

A large amount of energy is needed to A large amount of energy is needed to start the reaction and to prevent it from start the reaction and to prevent it from

running out of control.running out of control.

Do it yourself application Do it yourself application for E=mcfor E=mc22

Solar Cookers

Solar HeaterSolar Lighting