Question

2. A copper ring, attached to the ceiling as shown in figure 1, swings back and forth through a region of strong homogeneous magnetic field (Waltenhofen's pendulum). It can be observed that the pendulum's oscillations are strongly damped once the copper ring enters or leaves the magnetic field. Explain this observation. You can use keywords rather than a long text to answer this question, but make sure you are precise. Figure 1: Waltenhofen's pendulum

Answer 1

This can be explained using Faraday law of electromagnetic induction and lenz’ law. According to faraday’s law when magnetic field through an area is changed there will be a generation of emf. This emf will resiist the cause of generation of emf and hence there is a damping force only when flux through the sphere increase or decrease.