Understanding the Physics
* Electromagnetic Induction: When a magnet is moved near a coil of wire (like a solenoid), it induces an electromotive force (EMF). This EMF drives an electric current through the coil.
* Lenz's Law: The direction of the induced current is such that it opposes the change that caused it. This is Lenz's Law.
* Galvanometer: A galvanometer is a device that detects and measures small electric currents. It has a coil suspended in a magnetic field. The coil rotates based on the interaction between the current flowing through it and the magnetic field.
Why the Deflection Changes
1. Moving Magnet In: When the magnet is moved into the solenoid, the magnetic flux through the coil increases.
* Lenz's Law dictates that the induced current will create a magnetic field opposing this increase.
* This means the induced current will flow in a direction that creates a magnetic field pushing against the magnet.
* The galvanometer coil will deflect in a specific direction.
2. Moving Magnet Out: When the magnet is moved out of the solenoid, the magnetic flux through the coil decreases.
* Again, Lenz's Law dictates that the induced current will create a magnetic field opposing this decrease.
* Now, the induced current will flow in a direction that creates a magnetic field pulling the magnet back in.
* The galvanometer coil will deflect in the opposite direction compared to when the magnet was moving in.
In Summary
The direction of the deflection in the galvanometer depends on the direction of the induced current, which is determined by Lenz's Law and the changing magnetic flux through the solenoid as the magnet is moved.
