# Induced EMF on a primary coil by a secondary coil

1. Oct 8, 2009

### KaiserBrandon

1. Derive an equation to find the induced EMF on an inner solenoid by a changing current on an outer solenoid.

2. Relevant equations
We're given the equation EoRMS=(No*Ai*(2*pi*f)*(permeability constant)*IiRMS)/Li for the induced EMF on the outer solenoid by a changing current in the inner. I need an equation to replace this for when it's the other way around.

3. The attempt at a solution
I have no idea where to even begin, I just need a hint as to how I should start.

2. Oct 9, 2009

### Andrew Mason

$$V_{induced} = -N\frac{d\phi}{dt} = -NA\frac{dB}{dt}$$