As far as i can tell Dave Wings misunderstanding seems to be thinking that "current" is power. He is saying that if 1 amp goes in, and 1 amp comes out, then no "energy" has been "lost".

Of course, this is incorrect, as previously mentioned. So, Lets assume Dave W is a moron, and try and explain it to him in simpler terms. For this, i am going to replace "current" with "weight" and "voltage" with "gravity" (height)

So Dave, concentrate, here comes the (not much) science!

Here is an escalator:

Normally used to move people up and down in buildings, they usually take electrical power and use that to move the steps fixed to a continuous conveyor. Hopefully you can see / understand roughly how they mechanically function?

Now, lets not power the escalator, but use the motor as a generator, and simply attach a lightbulb to the wires of the motor.

Statically, nothing will happen, because the mass of the conveyor is balanced (with say 30 evenly weighted steps hanging on each side of the pulley that the motor is attached too).

But now, lets put a 50kg weight on a step on the top side. Now the system is unbalanced, and the converyor will start to move, turn the generator and light the lamp. Until of course, that weight gets to the bottom of the escalator and slides off. Att which point the steps will stop turning and the lamp will go out.

With me so far?

Now, instead of putting just one weight on the steps, lets keep putting them on. Everytime a "new" step comes up and around, lets put a 50kg weight on it. Now the system keeps turning, we keep adding weights, and they keep falling off the bottom one at a time. The lamp is lit all the time, as the steps keep turning. But we are not changing the weights in any way,just like your electrical circuit doesn't change the "Current" in any way, and yet power IS being extracted from the system.

In the case of our weight powered escalator, the power we can generate depends on the mass of the weights we add, and how far they can fall under the force of gravity. Add more weights or add them higher up and more work is done. In effect, the weights are the "Current" and the height they come down from the "Voltage difference". In all cases, if you stop adding weights, say because you are tired, the system will stop and no power will be generated. And in all cases, the weights (the current) are not changed by the process, just moved to a different (lower) location, and some other entity will need to add external "power" to keep the process running (in this case, you, carrying the weights back up to the top one at a time)

Hepefully, this mechanical analogy might help you understand that Power or Work Done, is the product of Current and Voltage (P = V x I), and that considering just current or just voltage is not sufficient to be able to establish the work done in circuit.