This is related to the electrical concept of resistance, but in the equation of resistance
$$R = \frac{ρ l}{A}$$
there's the cross-sectional area $A$ of the conductor.
Now if the conductor is a grating
then what's the cross-sectional area of such "flat" object? Is it the area of the object itself?
This is the second Ohm's law.
It's related to electric wires.
$A$ would be the section of the wire, which is usually the area of a circumference.
I believe your question is meaningless since you're understanding $A$ as the normal area of a geometric shape.
That law is related to electric wires.