 Hello everyone, myself Sanjay Utke, assistant professor, department of electronics engineering, Valchand Institute of Technology, Solapur. Today, we are going to discuss specific resistance short circuit open circuit. Beginning outcome at the end of this session, students will be able to analyze specific resistance short circuit open circuit resistance, specific resistance short circuit open circuit assignment references. Resistance, the electrical resistance of an object is a major of its opposition to the flow of electric current. The inverse quantity is electrical conductance and is with which an electric current passes. Electrical resistance is analogous to the mechanical friction. The unit of electrical resistance is the ohm, while electrical conductance is measured in cement. The resistance of an object depends on the material it is made of. Objects made of electrical insulators like rubber tend to have very high resistance and low conductivity, while electrical conductors like metals tend to have very low resistance and high conductivity. This relationship is quantified by resistivity or conductivity. The nature of material is not the only factor in resistance and conductance. However, it also depends on the size and shape of an object. The resistance denoted by capital R of an object is defined as the ratio of voltage V across it to current I through it, while the conductance G is the reciprocal of the resistance. So, R is equals to V upon I. So, conductance G will be is equal to I upon V or I upon R. For a wide variety of materials and conditions voltage and current are directly proportional to each other. Therefore, R resistance and G conductance are constants. Relation to resistivity and conductivity. The resistance of a given object depends primarily on two factors, what material it is made of and its shape. For a given material the resistance is inversely proportional to the cross sectional area. For example, a thick copper wire has lower resistance than an otherwise identical thin copper wire. Also for a given material the resistance is proportional to the length. For example, a long copper wire has higher resistance than an otherwise identical short copper wire. Here we are taking the example resistance. Here the length is given by small l whereas, it is a cross sectional area is given by capital A. Resistivity or specific resistance of a given substance is given by R is directly proportional to the length and inversely proportional to the area. This can be mathematically represented as R is equal to rho L upon A, where rho is constant depending on the nature of the material of the conductor and it is known as its specific resistance or resistivity. If length is equals to 1 meter and area is equal to 1 square meter then resistance is equals to resistivity. Hence specific resistance of a material may be defined as the resistance between the opposite faces of a meter cube of that material. In the SI units, in SI systems the unit for the resistivity can be derived from the equation rho is equal to A area into resistance divided by length and it is equals to ohm meter. Hence the unit of resistivity is ohm meter. If length is in centimeter area in centimeter square then rho its unit will be ohm centimeter short circuits. Two points of circuit are connected together by a thick metallic wire to be short circuited since short has practical zero resistance. It gives rise to two important facts. First one, no voltage can exist across it because V is equal to I into R, I is equal to I into resistance is 0 it is 0. Current through it called short circuit current is very large theoretically infinite. Shorts in a series circuit since a dead or solid short has almost zero resistance it causes the problem of excessive current which in turn causes power dissipation to increase many times and circuit components to burn out. Open circuit voltage abbreviated at OCV or VOC is the difference of electrical potential between two terminals of a device when disconnected from any circuit. There is no external load connected no external electric current flows between the terminals it is sometimes given the symbol VOC. The open circuit voltages of a batteries and solar cells are often quoted under particular condition, state of charge, illumination, temperature, etcetera. Open circuits two points are said to be open circuited when there is no direct connection between them. Obviously an open represents a break in the continuity of the circuit due to this break. First one resistance between the two points is infinite, second there is no flow of current between two points. Question the resistors of the question an aluminum wire 7.5 meter long is connected in parallel with a copper wire when a current of 5 ampere is passed through the combination it found that current in aluminum wire is 3 ampere diameter of aluminum wire is 1 mm determine the diameter of the copper wire resistivity of copper wire and aluminum wire is given. Now let us use the subscript 1 for aluminum wire and 2 for copper wire. So, R 1 is equal to rho rho 1 L 1 upon A 1 R 2 is equal to rho 2 L 2 upon A 2. So, dividing this R 1 upon R 2 R R 2 upon R 1 is equal to rho 2 upon R 1 into I 2 upon R 1 into A 1 upon A 2. Remember ratio of R 1 and I 2 is not given, but it is given in terms of the currents. Now if V is common voltage across the parallel combination of aluminum copper wire V is equal to I 1 R 1 is equals to I 2 R 2. So, R 1 upon R 2 is equals to I 2 upon I 1 which is two-third. So, in the above in this then instead of using R 1 and ratio of R 1 and R 2 we are using in terms of I 2 and I 1. So, we can find out A 1 is equal to pi d square upon 4 comes out to be pi by 4 mm square. Substituting this in the equation number 1 this is equation number 1 we get the area for the copper wire and then once you got the area we got the diameter also. Thank you.