Basic Electrical Engineering

From the name we can guess that superconductors are such conductors which have a very high conductivity (theoretically infinite) or zero resistance.  Usually in all conductors there are obstacles for electrons to flow like, collisions with other atoms of the material, repulsive forces between electrons (as we know like charges repel each other), impurities of the conductors, thermal disturbance created by temperature increase of the conductor etc. In a superconductor these obstacles are eliminated to have a perfect conduction. 

Copper effect: In a superconductive state, electrons are paired together to help each other maintain a significantly higher velocity through the medium.   

 

Superconductivity with years

History: Superconductivity was first discovered in 1911 but until 1986 it was of no use as it was only attainable at 23K (=-250C). In 1986 physicist Alex Muller and George Bednorz increased the temperature to 30K by using Lanthanum barium copper oxide. After few months of the same year professor Paul Chu and Man Kven Wu raised the temperature to 95K using a superconductor of Yttrium barium copper oxide.

In a temperature-resistance curve of a metal (such as copper) the resistance gradually increases with the increase of temperature. Temperature has a profound effect on resistance and hence it is important that we determine a method to find the resistance at any temperature within the limit of operation.  Although the temperature-resistance curve is not a straight line, we draw a best fit straight line to find the resistance at normal operating temperature range.

Two or more electrical elements are connected in series if they have only one common node in between and no other electrical element is connected to that common node. So there are two conditions for being in series:

To illustrate this lets have a look to the following circuit:

Series Circuit

In this circuit resistor R1 and R2 are in series as they have only b point common in between them and no other current carrying electrical element is connected at node b.

As there is no voltage source connected in between a series circuit, the voltage is shared among the resistors according to their values. So the ratio of voltage and resistor becomes constant and current does not change in the series circuit. For example see the following circuit:

Current is same throughout a series circuit

In this circuit, at R1, R2 and R3 voltage will be shared according to their resistance as there is no other voltage source in between them.  

Total sum of their resistance = (6+3+1) Ω = 10 Ω

So, according to ratio: for 1 ohm resistance voltage will be = (20 / 10) volt = 2 V

Therefore, Voltage of R1 = 6 x 2 V = 12 V,

                Voltage of R2 = 3 x 2 V = 6 V

                Voltage of R3 = 1 x 2 V = 2 V

Total voltage = (12 + 6 + 2) V = 20 V = Voltage of the source.

Now let’s find the current in all the resistors.

Current through R1 = (Voltage of R1 / Resistance of R1) = (12 V / 6 Ω) = 2 A

Current through R1 = (Voltage of R2 / Resistance of R2) = (6 V / 3 Ω) = 2 A

Current through R1 = (Voltage of R3 / Resistance of R3) = (2 V / 1 Ω) = 2 A

So its clear that, current through a series circuit remains same throughout the circuit. But the voltage of the circuit drops and is shared by the resistors or electrical elements of the circuit.