Electromagnetic wave, intensity, electric field problem

[ashleyd]

Homework Statement

Instead of sending power by a 850 kV, 1100 A transmission line, one desires to beam this energy via an electromagnetic wave. The beam has uniform intensity within a cross-sectional area of 80 m2. The speed of light is 3×10^8 m/s and the permeability of free space is 4×10^-7 T · m/A.
Find the rms value of the electric field.
Answer in units of kV/m

Homework Equations

P=IV
poynting vector = S = EB/mu0
Not sure if the following equations are relevant:
Power = I/Area
S=(E^2)/mu0*c

The Attempt at a Solution

I have tried using the formulas above, along with changing the kv to v
the answers i have gotten through this that are incorrect include:
18774.62904
593705.9
2099.06734
66378.33756

 

[gneill]

$$<S> = \frac{E_o^2}{2 \mu_0 c}$$

Where <S> is the time averaged magnitude of the Poynting vector for a plane wave.

What value did you calculate for <S>?

 

[ashleyd]

The value I got for S, without converting kV to V was 11687.5

 

[gneill]

Okay, convert to watts/m² and use the given formula to solve for E_o.