# Rate of Energy Transfer

1. Dec 3, 2015

### lloyd21

1. The problem statement, all variables and given/known data
It is fairly easy to produce a static magnetic field of 0.050T in the lab. If an EM wave could be produced with maximum magnetic field, Bo = 0.050T

a) what would be the rate of energy transfer (W/m2) ?

b) what would the corresponding maximum electric field be?

Note * Air "breaks down" at E = 3 x 10^6 V/m, that is sparks will jump across such a field.

2. Relevant equations
B= E / c
c = speed of light in vacuum

3. The attempt at a solution
0.050T (3.0 x 10^8 m/s) = 1.5 x 10^7 (electric field ?)

2. Dec 3, 2015

### haruspex

What about (the 'microscopic' version of) Poynting's theorem?

3. Dec 5, 2015

### lloyd21

Im not familiar with that?

4. Dec 5, 2015

5. Dec 5, 2015

### lloyd21

S= (1/Mo)(E)(B) ?
whats the S, and why is there a not about the air break down

6. Dec 5, 2015

### haruspex

S is the Poynting vector, and it's a cross product of E and B. But look a bit further down and you will see an expression for energy density. I thought that would be relevant to the question. Of course, that form is for a vacuum. Maybe you need a variant for air.

I don't think the note about air breakdown is relevant to answering the question. More likely it is for understanding the inference of the answer.

Having said all that, I'm no expert in this area.