Electro magnetic Induction problem. Simple one, but plz check wehre I am wrong.

chound

1. The problem statement, all variables and given/known data

A magnet moving down, goes through a coil and exits it below. Plot the graph showing variation of induced emf in coil with time.

2. Relevant equations

emf = - Flux/Time

3. The attempt at a solution
As the magnetic field B increases, emf becomes more and more negative.
Then while leaving, B decreases, emf becomes more and more positive.

Hence

The emf is first negative, forms a V shape in the negative emf region and then an inverted V in the positive emf region when it leaves.

4.Answer in the textbook
The emf is first positive ... in other words just the opposite of what I said.

Where did I go wrong ?

dimensionless

From what two points are you measuring the emf?

chound

From either ends of the coil

Axiom_137

Isn't the "B" in this system a vector?

(Those tricky vectors...)



~A137

chound

Ya. But how will that matter?

chound

I think I get it now.
Initially B and Area vectors are antiparallel, so flux is negative. Hence, the induced emf is positive.