If `rho` pis the resistance in ohm of a centimeter cube, generally called the specific resistance of the substance constituting the conductor, the resistance r of the layer containing "a" cubes is given by

Options

A. `1/r = (1)/(rho) + (1)/(rho)+….`
B. `1/r =(1)/(rhoa)+ (1)/(rhoa)+…`
C. `r=a//rho`
D. `r= rho + rho +….`

Answer

A

Explanation

Reciprocal of resistance is conductance. We can add the conductance and not resistance.
Hence `1/tau = 1/rho + 1/rho +……..`