Magnetism and Electromagnetism
A permeable substance is one

Which is a strong magnet
Which is a bad conductor
Through which the magnetic lines of force can pass very easily
Which is a good conductor

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Magnetism and Electromagnetism
Main causes of noisy solenoid are

strong tendency of fan out of laminations at the end caused by repulsion among magnetic lines of force
Both of the listed here
None of these
uneven bearing surface, caused by dirt or uneven wear between moving and stationary parts

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