- #1
niko_.97
- 18
- 4
If we have a some wire (length L) with a PD of V from one end to the next and a current I moving along it we can work out the Poynting vector. It's pointing radially inwards and so tells you the energy per unit time per unit area flowing into the the surface of the wire.
What I don't understand is how the energy can be passing into the wire from the outside? At first I was thinking the fields outside carry the energy in, but that just makes it even worse because it would imply that the fields are generate outside the wire, away from the charge and current which makes even less sense (not to mention the E field is zero outside). My professor told me that it can't be the fields because it's a statics problem. Though I didn't really understand his explanation for what the actual meaning of the poynting vector here is. I know it's defined as the energy passing per unit time per unit area, but what is carrying it in a problem where the fields are static?
What I don't understand is how the energy can be passing into the wire from the outside? At first I was thinking the fields outside carry the energy in, but that just makes it even worse because it would imply that the fields are generate outside the wire, away from the charge and current which makes even less sense (not to mention the E field is zero outside). My professor told me that it can't be the fields because it's a statics problem. Though I didn't really understand his explanation for what the actual meaning of the poynting vector here is. I know it's defined as the energy passing per unit time per unit area, but what is carrying it in a problem where the fields are static?