Superconductivity Video Lecture - Civil Engineering (CE)

what is a superconductor the present age
is the age of electricity we use
electricity to light the lights of our
houses streets etc devices like
television or a computer etc operate
with the help of electric current
thus electricity plays a very important
role in our daily life when we analyze
the devices which operate on electricity
we find that some amount of electricity
is always lost in the form of heat
let us discuss how when we analyze the
devices we find that they are composed
of vibrating positive ions and free
electrons these vibrating positive ions
offer resistance to the flow of free
electrons in the form of collision this
causes the loss of energy in the form of
heat note that about 20% of electricity
generated worldwide is wasted due to the
resistance of via and device so you can
imagine how much electricity we can save
if we can reduce the resistance of the
material in 1911 Dutch physicist heike
kamerlingh onnes discovered that under
certain conditions some materials do not
show any resistance such materials with
zero resistance are known as
superconductors thus we can say that
superconductor is a material that has
zero electrical resistance let's now
discuss the condition under which the
material shows the property of
superconductivity when we keep
decreasing the temperature of a material
we see that the free electrons stop
colliding with the ions as a result the
resistance of the material also
decreases to zero
and it starts behaving like a
superconductor the temperature at which
the electrical resistance of a material
drops to zero is called critical
temperature let us now analyze the
behavior of a superconductor when placed
in a magnetic field when we place a
superconductor in the magnetic field we
see that the magnetic field bends around
the superconductor as it is not able to
pass through it thus the superconductor
behaves like a perfect diamagnetic
material now if we keep increasing the
intensity of the magnetic field we see
that a stage comes when the magnetic
field penetrates through the
superconductor thus destroying its super
conductivity the magnitude of magnetic
field that which the superconductor
loses its super conductivity is known as
the critical magnetic field for a
superconductor it is given by two N's
law which is where HC is the critical
magnetic field at temperature T H o the
critical magnetic field at a temperature
of zero Kelvin T the temperature in
Kelvin and TC the critical temperature
in Kelvin the graphical representation
of x law is where the region inside the
curve represents the superconducting
phase and the region outside the curve
represents the normal phase of the
material let us now analyze the behavior
of a superconductor when an electric
current is passed through it let us pass
an electric current over the
superconductor now if we increase the
density of current we see that above
some specific current density the
superconductor loses its super
conductivity and starts behaving like a
normal material the current density
above which the superconductor loses its
super conductivity is called the
critical current density
it depends upon the property of the
superconductor geometry of the
superconductor temperature and applied
magnetic field thus high temperature
high magnetic field and high current
density are the three conditions that
can break the super conductivity of a
material if we draw a graph with the
parameters temperature current density
and magnetic field then the region
within the boundary represents the super
conductivity of a material and the
region outside the boundary represents
the normal phase of a material related
terms are