A magnet dropped through a vertical solenoid will fall at a rate that is slower than gravity, and will induce an electric current within the solenoid. which physics principle explain these phenomena ?
The phenomena you described can be explained by two fundamental principles in physics: the principle of electromagnetic induction and the principle of Lenz's law.
First, let's understand the principle of electromagnetic induction. According to this principle, a changing magnetic field can induce an electric current in a conductor. When a magnet is dropped through a vertical solenoid, the magnetic field inside the solenoid changes as the magnet moves.
Secondly, Lenz's law states that the induced current will produce a magnetic field that opposes the change in magnetic field that caused it. In simpler terms, the induced current creates a magnetic field that opposes the motion of the magnet.
Now, let's break down how these principles explain the phenomena you described:
1. Slower falling rate than gravity: As the magnet falls through the solenoid, the changing magnetic field induces a current in the solenoid. According to Lenz's law, this induced current produces a magnetic field that opposes the motion of the magnet. The interaction between the induced magnetic field and the magnet's field causes a drag force that counteracts the force of gravity. This drag force slows down the magnet's fall, resulting in a slower falling rate than gravity alone.
2. Induced electric current: The changing magnetic field induces an electric current within the solenoid. This current arises due to the motion of the magnet through the solenoid's coil. The induction occurs because the magnetic field lines of the magnet intersect with the coil, creating a changing magnetic flux. According to the principle of electromagnetic induction, this changing magnetic flux induces a current in the solenoid, which can be measured as an electric current.
In summary, the phenomena of a slower falling rate and induced electric current in a vertical solenoid when a magnet is dropped can be explained by the principles of electromagnetic induction and Lenz's law.