Magnetism and Electromagnetism
The force between two long parallel conductors is inversely proportional to

Product of current in two conductors
Distance between the conductors
Radius of conductor
Current in one conductor

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Magnetism and Electromagnetism
Main causes of noisy solenoid are

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

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