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I have added a picture of the secondary side of a transformer (crude drawing) in my understanding a battery causing current to flow through a difference in electrons.

In this scenario with A/C current if both sides are at say 240v then what would cause the current to occilate? If neither side is connected to ground so there isn't a lower potential difference.

enter image description here

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    \$\begingroup\$ I have no idea of what you are talking about... \$\endgroup\$ – Eugene Sh. Nov 14 '16 at 15:51
  • \$\begingroup\$ In isolated transformers if neither side is connected to ground how would current flow? \$\endgroup\$ – Dominic Burton Nov 14 '16 at 15:52
  • \$\begingroup\$ If there is no closed circuit - it won't... Doesn't matter ground or not. \$\endgroup\$ – Eugene Sh. Nov 14 '16 at 15:53
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    \$\begingroup\$ If the secondary voltage of the transformer is 240 Volts, there will be 240 Volts between the end of the secondary, whether one end of the secondary is grounded or not. Voltage is measured between two points - Ground need not be involved. \$\endgroup\$ – Peter Bennett Nov 14 '16 at 16:45
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    \$\begingroup\$ How would a battery powered radio work if it needed a galvanic connection to ground? How did voyager manage to send radio comms to earth from the edge of the solar system - did it have a long trailing wire? \$\endgroup\$ – Andy aka Nov 14 '16 at 17:42
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If you connect a solenoid-wound inductor to an AC source, an alternating magnetic field will be generated about the coil which will build to some maximum strength in one direction, will fall to zero, will build up again in the opposite direction, will fall to zero, and then the cycle will begin anew.

Now, if you place another coil close to, and with its axis not aligned orthogonally with the one which is generating the varying magnetic field, the field will pass through the second coil and will induce/generate a voltage difference which will appear across the ends of the wire comprising the second coil.

If those ends are not connected to anything, the voltage induced in the coil will have no work to do, hence there'll be no current in the secondary coil.

If the ends are connected together, then charge will flow and there'll be current in the secondary.

Notice that nowhere has "ground" been mentioned, and yet everything worked, OK?

Now let's move on...

Say we have three of the dual solenoid circuits, one which outputs 1 volt, AC, one which outputs 2 volts, AC, one which outputs 3 volts, AC, and that we've connected one end of their secondary coils together and have let the other ends float.

If we connect one lead of an AC voltmeter to the place where the three ends were connected together, then we can use the other lead to probe the floating terminals and we'll find that one of them outputs 1 volt, another outputs 2 volts, and the other 3 volts.

The place where they're connected together is called "ground", by convention, since it's where the measure of everyone's tallness was measured, in antiquity and to this day.

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