Answer
The current through the water layer is $~~9.41~mA$
Work Step by Step
We can find the cross-sectional area of the water layer:
$A = \pi~[(2.50~mm)^2-(2.00~mm)^2]$
$A = (2.25~\pi)~mm^2$
$A = 7.07\times 10^{-6}~m^2$
We can find the resistance of the water layer:
$R = \frac{\rho~L}{A}$
$R = \frac{(150~\Omega \cdot m)(800~m)}{7.07\times 10^{-6}~m^2}$
$R = 1.70\times 10^{10}~\Omega$
We can find the current:
$i = \frac{V}{R}$
$i = \frac{160\times 10^6~V}{1.70\times 10^{10}~\Omega}$
$i = 9.41\times 10^{-3}~A$
$i = 9.41~mA$
The current through the water layer is $~~9.41~mA$
