Self-inductance of an air core solenoid increases from 0.01 mH to 10 mH when an iron core is introduced in it. What is the relative magnetic permeability of iron?

Explanation

Self-inductance is proportional to the permeability of the core. So, we get,
`(L)/(L_(0))=(mu)/(mu_(0))=mu_(r)ormu_(r)=(L)/(L_(0))=(10)/(0.01)`
`therefore mu_(r)=1000`
Hence relative magnetic permeability of iron is 1000.