Question

Assume that the pictured magnet is being moved into the solenoid. If the polarity of the magnet is reversed and then moved into the solenoid, what happens?

Answer 1

Answer:

The direction of the induced emf is revered, and hence the direction of the induced current.

Explanation:

When the polarity of the magnet is revered, the direction of the magnetic field is also reversed, and therefore, according to Faraday's law

$\varepsilon = NA\dfrac{dBcos(\theta)}{dt}$

$\varepsilon = -NA\dfrac{dBcos(\theta)}{dt}$

since the magnetic field changes sign from $B$ to $-B$.

Hence, the effect is that the direction of the emf induced is reversed, which also reverses the direction of the induced current in the solenoid.

P.S: The cause of confusion here is the direction of magnetic field lines from the magnetic, and so you must remember that field lines begin at the north pole and end at the south pole.