Electrical resistance and conductance-

The electrical resistance of an electrical conductor is the opposition to the passage of an electric current through that conductor; the inverse quantity iselectrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical notion offriction. The SI unit of electrical resistance is the ohm (Ω), while electrical conductance is measured in siemens (S).

The resistance (R) of an object is defined as the ratio of voltage across it (V) to current through it (I), while the conductance (G) is the inverse:

$R = {V\over I}, \qquad G = {I\over V}, \qquad G = \frac{1}{R}$ .

Relation to resistivity and conductivity-

he 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. The resistance