Originally posted by StellarX
Objection 3: although some books say that you have to have a complete conducting loop before a current can exist, that is just another misconception.
Electrons do not travel across the insulating gap in a capacitor nor do they jump across the space between the primary and secondary windings of a
transformer. This is so even when the energy source is a battery; I have constructed circuits like those in figure 2 that show that the lamp lights up
briefly when the switch is closed. No matter how the energy travels in those examples, it must be able to get through empty space. (It is true that if
you want to maintain a steady current in a circuit, then a continuous conducting loop is required.)
I don't know where this is from, but it's a complete misunderstanding in how electricity works.
This person is confusing the source of the electricity with the circuit, when they say "energy has to travel trough empty space in a power source, so
why should circuits have to be closed loops" (summed up)
While electricity does travel through a circuit, which therefore has to be a closed loop, it does NOT travel through the power source!
The power source is always just the DIFFERENCE between two POTENTIALS.
And to use this potential power, you have to give it something to travel through, like a circuit.
Energy does not flow through a battery. But it does flow from one potential in the battery to the other THROUGH the circuit!
While i hate water analogies, it might help here.
Imagine two barrels. One with no (or little) water, and another full of water. The difference in water level is the potential. If you connect these
two barrels with a tube, the water will flow from the one with the higher level of water to the one with the lower amount of water. When both drums
have the same level, the difference in potential is ZERO, and no more water can flow through.
It's the same thing with power sources. A battery consists of two different potentials in one neat package. It needs a wire or a circuit for the
energy to flow through (tube in the water analogy).
The only power transfer between the two potentials is THROUGH the circuit (tube) and not somehow magically between the two drums through empty space.
Still, the energy flow from one potential to the other can power an electric motor (or a water wheel in the water analogy).
The quote is a good example of what happens when people with little or no knowledge about electricity try to explain it.
[edit on 26-12-2007 by deezee]