How to Find the Potential Energy of a Cloud?

[boneill3]

Homework Statement

Assuming the maximum electric field sustained by dry air in a cloud is 3x10^6 Vm^-1
And a distanceof 1000 meters between Earth and cloud. The cloud is 4km long and 1 km wide. ausume uniform eletric field. Find the potential difference.

Homework Equations

$V=Ed$
$\mu = \frac{1}{2}(\epsilon_{0}\times E^2)$

The Attempt at a Solution

$\mu = \frac{1}{2}(\epsilon_{0}\times E^2)$
$3\times 10^6 = \frac{1}{2}(8.85\times 10^-12\times E^2)$
$E=\sqrt{\frac{3\times 10^6}{\frac{1}{2}(8.85\times10^-12\timesE^2)}}$
$E = 8.23\times10^8$

using $V=Ed$
$E = 8.23\times10^8 \times 1000$
=8.23x10^11 volts


is this right?

 

[cepheid]

Homework Equations

$V=Ed$
$\mu = \frac{1}{2}(\epsilon_{0}\times E^2)$

You don't need the second formula (which is for the energy stored in an electric field, I believe. The first equation, along with the given information, should be enough to solve the problem.

$\mu = \frac{1}{2}(\epsilon_{0}\times E^2)$
$3\times 10^6 = \frac{1}{2}(8.85\times 10^-12\times E^2)$

Why have you plugged in the value of the electric field, E, for mu? The electric field, E, is already given to you. You don't need to solve for it.