Figure 23.21 shows a vertical iron rod with a wire coil of...

Name: Problem 47, Chapter 23: Pearson Physics
Uploaded: 2023-03-24T03:26:37-08:00
Duration: 4 min 12 s
Channel: Supratim Pal
Description: Figure 23.21 shows a vertical iron rod with a wire coil of many loops wrapped around its base. A metal ring slides over the rod and rests on the wire coil. Initially, the switch connecting the coil to a battery is open, but when it is closed, the ring flies into the air. Explain why this happens.

Figure 23.21 shows a vertical iron rod with a wire coil of many loops wrapped around its base. A metal ring slides over the rod and rests on the wire coil. Initially, the switch connecting the coil to a battery is open, but when it is closed, the ring flies into the air. Explain why this happens.

Key Concepts

Electromagnetic Induction

This concept explains how a changing magnetic field can induce an electromotive force (emf) and, consequently, currents in nearby conductors. When the coil is energized, its magnetic field increases rapidly, leading to a change in flux through the nearby metal ring and inducing an eddy current within it.

Lenz's Law

Lenz's Law states that the direction of any induced current will be such that it opposes the change in magnetic flux that produced it. In this scenario, the induced current in the metal ring creates its own magnetic field that opposes the coil's increasing field, resulting in a repulsive force that propels the ring upward.

Magnetic Fields of Current-Carrying Coils

When current flows through a coil, it generates a magnetic field. The structure of the coil, especially when wound around an iron rod, focuses and strengthens this field. The produced magnetic field is critical in interacting with and inducing currents in nearby conductive objects such as the metal ring.

Magnetic Forces on Induced Currents

Conductors with induced currents experience forces when placed in external magnetic fields. This force arises from the interaction between the magnetic field created by the induced current (due to electromagnetic induction and Lenz’s Law) and the original magnetic field of the coil, leading to mechanical motion, such as the upward movement of the ring.

Transcript

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