# Direction of the induced current and polarity

1. Apr 17, 2013

### fishingspree2

1. The problem statement, all variables and given/known data
http://img805.imageshack.us/img805/6030/82154948.png [Broken]
Find Vemf (between points 1 and 2) and it's polarity at t = 0.
I have omitted details because my question is specifically on the polarity.

2. Relevant equations
Lenz's law:
An induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux.

Vemf = -dΦ/dt

3. The attempt at a solution
This is a worked out example in my textbook. We first find the flux Φ and Vemf which are function of time. We compute dΦ/dt at t = 0. Then Vemf = -dΦ/dt.

We find that dΦ/dt > 0, so the magnetic field B is increasing. To counter-act this change, I must be in the direction given in the picture. Everything is ok at this point.

Now here is where I get lost. My textbook says:

I thought I always is from the higher potential to the lower potential. Which should make terminal 1 at a higher potential than terminal 2 considering the direction of I. It seems like the textbook have it reversed.

What am I missing?

Last edited by a moderator: May 6, 2017
2. Apr 17, 2013

### fishingspree2

Is it a matter of conventional current vs electrons flow?