Introduction :
Superconductivity is a condition in metals and alloys at low temperature involving
zero electrical resistance. Electric current will persist indefinitely without
any driving voltage. Here there is no resistance in the path of electrons. If
in a metal extra energy is given to the electron by using external electric
field in a particular direction, then electrons will move such as if there is
no resistance in the path. If the forces on the electron is such that they move
in a closed loop, this will act like a superconductor. This stage may be defined
as artificial superconductivity.
Theory :
Electrets are the permanent polarized dielectric material, which are made by
cooling a dielectric material in the high electric field. These materials can
be easily handled. Electrets have opposite charge on its surface the electric
field of the electrets are shown in fig.1. From the electrostatic theory, it
is known that when a metallic cylinder is placed in the electric field as shown
in the fig.2, the electric field intensity inside the cylinder will be zero.
Three electrets are placed with hollow cylinder fitted at the centre and a metallic
rod passing through the cylinder.
For easy understanding, the metallic rod may be replaced by a glass tube in
which negative particle is placed and the position of the particle at different
time is X1, X2, X3, X4, X5 as shown in fig.3. When the particle is at position
X1 the force due to negative charge of electret ET1 will be in perpendicular
direction and positive charge of electret ET2 will move the particle in forward
direction. When the particle reaches at X2 position then it will move in forward
direction by the forces due to negative charge of electret ET1 and positive
charge of electret ET2. When the particle reaches at position X3 then it will
move forward by the force due to negative charge of electret ET1. When the particle
reaches at position X4, the forces due to positive and negative charges of the
electret ET2 will be zero due to metallic cylinder fitted at the centre. Now
the forces due to the negative charge of the electret ET1 and positive charge
of the electret ET3 will move the particle forward. When the particles reaches
at position X5, behaviour of the particle will be similar to that at position
X1 and particle will move forward by the force due to positive charge of electret
ET3. When the path of the particle is made into circular form then this particle
will move in a closed path as shown in fig.4. The electric current in the metallic
rod will flow in direction opposite to the path of negative particle.
The PDF document with complete text, images and equations can be downloaded using the download link below
