1. Transformers

2. And you

3. What are they? Transformers change the voltage of a current
From high voltage to low voltage
Or from low voltage to high voltage

4. How do they work??
If you were thinking induction – you were correct!!!!
Recall Faraday’s law: Δϕ / Δt = EMF
We discussed this in terms of a simple loop of wire
But if we have a coil of wire – we have to consider it is a series of loops – all impacted by the magnetic field

5. So Faraday’s law applied to a coil:
EMF = -N (Δϕ / Δt)
Where “N” pertains to the # of coils of wire
The “-” sign is present because the induced current creates a magnetic force that opposes the applied force (think about the sliding bar example) – no need to focus on this point right now…

6. What really mattes here is this:
The more coils I have, the greater the induced EMF (given the same magnetic flux)

7. What can we do with this fantastic knowledge???
Well we can start by passing a current through a coil of wire that is wrapped around a metal core (to contain the B field)
Then we coil another wire around the iron core and induce a current through that second coil. If we want the induced EMF to go up, we simply coil more wire in the second coil than we have in the first coil.

8. Like this:

9. So what about the math here?
E secondary coil / E primary = NS / Np
Recall that you need a ΔB to induce an EMF
Therefore this requires an alternating current in the primary coil (a current that changes)

10. In summary Ns > Np = V  = step up transformer
Ns < Np = V = step down transformer
And no – a step up transformer is not free energy. P in = P out
P = VI so if V goes up, I goes down