RESISTANCE:

It is defined as the property of a substance due to which it opposes the flow of electricity (electrons) through it.

Unit : ohm (Ω)

R ∞ l / A

R = ρ l/A

ρ - resistivity (Ωm) or Specific resistance

CONDUCTANCE:

It is reciprocal of resistance.

G = 1 / R = A / (ρ l) = σ A/l

σ = Conductivity (mho/m) or Specific Conductance

Unit : mho

Ohm’s Law:

The ratio of potential difference (V) between any two points on a conductor to the current (l) flowing between them, is constant, provide the temperature of conductor does not change.

V / I = constant

V / I = R