The motion of copper plate is damped when it is allowed to oscillate between the two poles of a magnet. What is the cause of this damping?

Answer

### Step-by-Step Solution:

1. **Understanding the Scenario**:
- A copper plate is allowed to oscillate between the poles of a magnet. This setup involves the interaction of the copper plate with a magnetic field.

2. **Magnetic Flux Change**:
- As the copper plate oscillates, it moves through the magnetic field. This motion results in a continuous change in the magnetic flux linked with the plate.

3. **Induction of Eddy Currents**:
- According to Faraday's law of electromagnetic induction, a change in magnetic flux through a conductor induces an electromotive force (EMF) in the conductor. In this case, the oscillating copper plate experiences a changing magnetic field, which induces loops of electrical currents known as eddy currents within the plate.

4. **Effect of Eddy Currents**:
- Eddy currents flow in such a way that they create their own magnetic fields. According to Lenz's Law, these induced currents will oppose the change that created them. Therefore, the eddy currents generated in the copper plate will produce a magnetic field that opposes the motion of the plate.

5. **Damping of Motion**:
- The opposition to the motion due to the eddy currents results in a resistive force that acts against the oscillation of the copper plate. This resistive force dissipates energy in the form of heat due to the resistance of the copper, leading to a damping effect.

6. **Conclusion**:
- The cause of the damping of the motion of the copper plate is primarily due to the generation of eddy currents, which oppose the motion of the plate and convert kinetic energy into thermal energy, thus bringing the plate to rest.