Power loss in sinusoidal electric fields

[JerryG]

Homework Statement

In my electromagnetics book, in the section that talks about loss tangents, the equation for average power dissipation per unit volume is P=(1/2)*J*E (W/m^3). What does the coefficient of 1/2 come from? Earlier in the book, it gave the differential power dissipation dP= J*E (W/m^3)

Homework Equations

J = current density.
E= electric field.

 

[gneill]

Is it possible that previously E was a constant value, and now E is the peak value of a sinusoid?

 

[JerryG]

Is it possible that previously E was a constant value, and now E is the peak value of a sinusoid?

That's it. It's the Erms ^ 2 that gives the 1/2.