The core used in transformers and other electromagnetic devices is laminated to

$A$ magnet is dropped down an infinitely long vertical copper tube.

Consider a metallic pipe with an inner radius of $1 \ cm$. If a cylindrical bar magnet of radius $0.8 \ cm$ is dropped through the pipe,it takes more time to come down than it takes for a similar unmagnetised cylindrical iron bar dropped through the metallic pipe. Explain.

Assertion: $A$ laminated core is used in transformers to increase eddy currents.
Reason: The efficiency of a transformer increases with increase in eddy currents.

$A$ bar magnet is released from rest coaxially along the axis of a very long,vertical copper tube. After some time,the magnet:

$A$ light disc made of aluminium (a nonmagnetic material) is kept horizontally and is free to rotate about its axis as shown in the figure. $A$ strong magnet is held vertically at a point above the disc away from its axis. On revolving the magnet about the axis of the disc,the disc will (figure is schematic and not drawn to scale)-