A small bar magnet is being slowly inserted with constant velocity inside a solenoid as shown in figure. Which graph best represents the relationship between emf induced with time

Options

A.
B.
C.
D.

Answer

C

Explanation

Initially `phi_(B)` increases as the magnet approaches the solenoid. Therefore, `epsilon` is negative and increases in magnitude when the magnet moves inside the solenoid. Increase in `phi_(B)` slows down and finally `phi_(B)` starts decreasing. Therefore e.m.f becomes positive and starts increasing. Only graph (c ) shows these characteristics. Also polarity of emf will charge when magnet starts coming out.