E=
2
mc
E=
2
mc
is everywhere!
E=
2
mc
Energy (in joules)
= Mass (in kilograms) X
The Speed of Light Squared
(in meters squared per second squared)
The big question???
How much energy
will one liter of
water yield if it is
converted entirely
into energy?
But Chemistry says matter cannot be
created nor be destroyed???
Lots
Neither
of energy
can
be
goes
No
it’s
Not!
2
E = mc tells you
destroyed
into making
but,
even
under
a
Matter
andhow
Energy
are
exactly
much
special
small mass
circumstances,
and it can
energy
given
two
forms
ofabe
the
same
either
also
be
can
got
back
turned
in
amount
of mass
thing!
some
into
theform.
other
contains.
The speed of light…
Light travels three hundred million meters in a
second i.e. 300,000,000 m/s
So (forgetting the units for now)
Energy = mass x (300,000,000)2
or E = m (90,000,000,000,000,000)
= m (9 x 1016)
That’s a
BIG
lot
.
Mass
What is the mass of 1 liter of water?
A liter of water is defined to have a mass of
one kilogram!
m=1
So, E = 1 (9 X 1016)
= 9 X 1016 Joules
What could we do
with all this
energy?
Energy & Power
A Joule is the effort required to push one kilogram
over a meter at an acceleration of one
meter/second2.
A Joule expended continuously for one second is a
Watt.
A liter of water, converted to energy
could power a 1 watt light bulb for…
9x1016 seconds, or 2.5x1013 hours
or ~3 billion years! (2/3 the age of the Earth)
A 100 Watt bulb…
would only stay lit for 2.5 x 1011 hours!
There are about 109 families on Earth
So let’s light 109 bulbs of 100 Watt power
for 250 hours…!
You
spend the same amount of energy
as a 100 watt bulb !
[ One joule is equal to about four food calories]
The downside
200,000 people have been killed by just 2 atomic bombs.
One Hydrogen Bomb could kill 50 times as many!
Most environment friendly
application
All our energy
comes from the
Sun!
The Sun has E=mc2
as its source of
energy.
Nuclear Fusion
When 4 hydrogen nuclei
are fused together into
1 helium nucleus,
energy is released in
the form of Light
photons and particles
called neutrinos.
But where does the mass come from?
Mass of 4 hydrogen nuclei is more than that
of 1 helium nucleus
So after fusion a little bit of mass is left over.
This mass deficit appears as the energy of
light and neutrinos.
A 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 =
2
mc
The Sun emits 4 x 1026 joules per second
How much mass does it
convert each second in
order to shine?
If the Lifetime of the Sun
is 1010 years, how much
mass would it need in that
time?
Use m = E/c2 !
How do you convert any mass to Energy
on Earth?
Scientists are trying to make a sun on the Earth
through fusion reactors that use hydrogen.
Hydrogen is the simplest & lightest element.
Hydrogen is abundantly found in water!
Hydrogen fusion has been tried and tested in Nature
and on Earth (in H-Bombs).
The only scientist that was able to
accomplish sustained nuclear fusion..
What are the barriers to attaining
nuclear fusion?
Hydrogen is a diffused gas and it is difficult to
get its nuclei close enough to fuse.
They start colliding into each other only at a
temperature of 15 million degrees C.
We need to keep it both hot & dense.
A large amount of energy is needed to start the
reaction and to prevent it from running out of
control.
Do it yourself application for E=mc2
Lighting
SolarSolar
Heater
Solar Cookers