Exploring the Impact of Disconnecting a Solenoid on Current Flow

[maxexeter]

QUESTION: I have two solenoids, one connected to a power supply so that current flows through the coil, and the other
connected to a galvanometer. When I disconnect the power supply in the left coil, current flows momentarily in
the right coil. Explain why and predict which way the galvanometer needle deflects.

Right now, we are not using any equations. The current in the solenoid in the left is moving downwards at the front, so the south pole is on the right (towards the solenoid on the right, which is connected to the galvanometer). We use the left hand rule, so please keep that in mind. There is no velocity, so I cannot see why there would be a change in current? Thanks for taking the time!

 

[jbsteele]

This phenomenon is known as electromagnetic induction. When the power supply in the left solenoid is disconnected, a changing magnetic field is created in the area around the two solenoids. This changing magnetic field induces a current to flow in the right solenoid, which is connected to the galvanometer. The direction of this induced current can be determined using the left-hand rule. Place your left hand so that your thumb is pointing in the direction of the current that was flowing in the left solenoid. Your fingers will curl in the direction of the induced current in the right solenoid. Therefore, the galvanometer needle will deflect in the same direction as your fingers are curling.