Would a simple electric generator based on magnetic induction( magnet moving near coils to produce current) work in vacuum? I mean if that generator would be connected to battery to charge it - moving magnet would cause electrons from coil to move into the battery but in vacuum there would be no electrons to replace these which moved from coil into the bettery. This is how I think of that. Can someone correct me or clarify if that is true or false?

  • 2
    $\begingroup$ Why would you think vacuum has anything to do with the presence of electrons in a conductor? $\endgroup$
    – paisanco
    Commented Sep 14, 2014 at 3:45
  • $\begingroup$ I think of it as that, battery storage electrons that flow from conductor to battery but electrons that will go and stay in that storage must have the source $\endgroup$
    – nbvn
    Commented Sep 14, 2014 at 3:53
  • $\begingroup$ The electrons don't enter the battery and never leave. $\endgroup$
    – paisanco
    Commented Sep 14, 2014 at 3:56
  • 2
    $\begingroup$ your coil must form a closed circuit - electrons moving from one end of the battery to the other under the influence of the changing magnetic flux. There would be as many electrons leaving one side of the battery as would enter the other, leaving no net change in charge. Whether the coil is surrounded by a vacuum has nothing to do with it. $\endgroup$
    – Floris
    Commented Sep 14, 2014 at 5:22
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    $\begingroup$ @Floris if "electrons move from one end of the battery to the other" how is it possible that "The electrons don't enter the battery and never leave" ? If a battery is charged does it not mean it has more electrons at one end that move when battery is "in use" to the other end ? $\endgroup$
    – nbvn
    Commented Sep 14, 2014 at 17:38

3 Answers 3


Yes. Why not?

The electrons entering the battery1 do not come from the air, or from anywhere else; they come from the wire which is "refilled" at the other end with electrons from that very battery.

As far as the charges are concerned, battery, generator and consumer (like a motor or light bulb) are constituting a closed system. Charges do not leak from it, and no new charges (electrons or ions) are entering it.2,3

As an aside: I personally have found that models of water circuits can help a lot in understanding electric circuits. Here is a list of corresponding items:

  • Wires -> garden hoses
  • Generators -> powered turbine pump (pushes water through the hose when powered)
  • Electric motor -> turbine driven by the water flow (can drive a motor, for example)
  • Battery -> spring-loaded piston immersed longitudinally in the hose: Water pumped in it from one side loads it and stores energy in it; as soon as the pump is removed/switched to neutral, and the water circuit closed, the spring-loaded piston pushes the water back, pulling water in behind itself, so that the same amount of water the piston pushes out must be flowing in behind it; until it is back in the unloaded position, like a depleted battery.
  • Capacitor: Behaves basically like a battery, both ways for plate capacitors, so it is modeled with a piston which can be loaded both ways.
  • Inductor: Turbine-powered flywheel.

The turbines (both for motors and pumps) have to be imagined not as propellers but as a locking impeller or paddle-wheel which cannot move when the water flow is blocked.

Incidentally, the turbine model lets us use generators as motors and vice versa, which is true for electricity as well.

The water flow model also corresponds nicely in another detail: It is true that an electric current starts to flow almost instantaneously after a circuit is closed (more precise, the electric field which makes it flow propagates with light speed); but the actual "flow speed" (drift velocity) of the electrons is remarkably slow (for example 0.000023 m/s for 1A in a normal wire). The electrons start to flow immediately (and "immediately" stop flowing when the circuit breaker triggers) because they are fairly incompressible in the wire. The same is true for water: It starts to flow "immediately", but the flow speed through the pipe is relatively slow. Water is incompressible, too.

1 paisanco was of course incorrect in his statement that "The electrons don't enter the battery and never leave". They certainly do; how else could there be a flow of electrons through the wire connecting both poles of the battery? The number of electrons leaving is quite exactly equal to the electrons entering though, because neither the battery nor the generator acquire an electrical charge over time.

2 This is describing an ideal battery.

3 Perhaps you are thinking of types of residential wiring which uses the earth to conduct current back to the power plant, so-called "Single Wire Earth Return".


Your thought is correct if you talk about an isolated system with a DC generator and a capacitor instead of a chemical battery. After the magnetic force moved some electrons through the generator from one side of the generator to the over the process get stopped because the electrostatic forces in the atoms of the capacitor rise exponential.

If you instead of a capacitor place a chemical battery it depends from the artfully work of chemists how long and with which potential difference you can shift electrons from one pol of the battery to the other. In the battery the electrostatic force of the generator acts on chemical compounds and change their electrical potential.

A third thing is it to have a grid of sources (generators) and sinks (consumers) which generate and contribute electrical current at the same time. The engineering knowledge is it to hold the balance between sinks and sources.


Logic dictates electrons exist throughout the universe/universes the magnetism of the generator draws aligns and drives the "electricity" to a usable form or energy some types of "batterys" generate electricity chemically and stripping electrons from atoms can be violent I think. We can live on this rock cause ultimately it's a big generator hanging in "space" tethered to an even bigger generator. And these things are using electrons and I want to understand how.


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