Let us consider a simple dc circuit consisting of a battery and a resistor connected by ideal wires. As we know, current starts to flow thorugh the resistor and heat is generated as a result of this current flow. We need to determine how this energy is transferred from the voltage source to the resistor. The answer, suprisingly, is that the ideal wires connecting the battery to the resistor carry no energy at all. Most of the energy flows around the ideal wires. This is because the electric field inside the wires is zero and according to the Poynting theorem, no energy can flow if the electric field is zero in any given region of space. However, a radial electric field exists outside the current carrying wires and hence energy flows parallel to the wires and gets converted to heat in the resistor.