Eddy Currents in Magnetic Fields: Copper/Aluminum vs Iron

[ananthu]

Homework Statement

It is given that when a copper or aluminium bar is set in oscillation in a magnetic field eddy currents are produced inside the bar. Should it be necessary that the bar should be made of a non-magnetic substance such as copper, aluminium etc.? Can it be a ferromagnetic substance like iron? When an iron bar is introduced in between the magnets, unlike an aluminium bar the former also gets magnetized. So, will the formation of eddy currents ,in any way, be affected due to magnetism produced in the bar?

Homework Equations

The Attempt at a Solution

 

[tiny-tim]

Hi ananthu!

Since no-one else is answering, I'll have a go …

I think it's because all materials have diamagnetism, but "magnetic" materials also have ferro- or para- magnetism, and that's much stronger …

eddy currents are a consequence of diamagnetism, but the effect gets swamped by the "ordinary" magnetism in "magnetic" materials.

 

[ananthu]

Thank you for your reply. But your reply has not served in clearing my doubts. My question is whether eddy currents will be produced at all in an iron bar? If so why in all examples, it is mentioned either as a copper bar or aluminium bar? Even in a speedometer, only an aluminium disc is used but not an iron or steel disc?