electromagnetism - Transformers - Why more coils in second coil causes more voltage

I am learning about magnetic induction and transformers.

1. 
   

   I have coil1 which uses AC to create an oscillating magnetic field.

   
   


2. 
   

   I have coil2 which has a voltage applied to it based on the magnetic field from coil1.

   
   

I just heard that if you have more coils in coil2 (the coil dependent on the oscillating magnetic field) you get a bigger voltage and this seems counter intuitive because:

1. 
   

   voltage is based on pressure and that pressure is coming from coil1 so how can it be bigger?

   
   


2. 
   

   wouldn't more electrons present in coil2 cause more resistance and thus make the voltage smaller?

   
   

How is it that with more coils you get a bigger voltage?

Answer

Expanding on Jan Dvorak's comment:

When you change the magnetic field inside a loop, an emf (electromotive force) will be generated. Now if you have two loops, each of these will experience the same e.m.f. When you put them in series, you have a coil with two loops, or two coils with one loop. No matter which way you look at it the voltage across them should be the same - V + V = 2V.

Notice that this doesn't mean you can get more current: as you pointed out, resistance will go up when you have more turns, but that doesn't matter unless a current is flowing. So the tricky thing here is that more turns in the secondary winding of a transformer will increase the voltage, but not the power.

In fact, the opposite happens. When current is allowed to flow in the secondary winding, it will cause a magnetic field that opposes the magnetic field that caused the current in the first place. If you have more turns, then you only need a little bit of current to create the opposing magnetic field.

So while the voltage goes up with more turns, the current you can generate goes down - not just because of resistance but because of inductance, or the ability of the coil to generate a magnetic field in response to a current.

The net result is that a transformer cannot generate power out of nothing - in fact they usually have efficiency (power conversion factor) well below 100%, which is in part why they get hot when you use them...