The core of any transformer is laminated so as to

$A$ copper ring is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet while it is passing through the ring is

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: $A$ bar magnet dropped through a metallic cylindrical pipe takes more time to come down compared to a non-magnetic bar with same geometry and mass.
Reason $R$: For the magnetic bar,Eddy currents are produced in the metallic pipe which oppose the motion of the magnetic bar.
In the light of the above statements,choose the correct answer from the options given below:

What should be the resistivity of materials used for electromagnets,and why?

$A$ sheet is placed on a horizontal surface in front of a strong magnetic pole. $A$ force is needed to:
$A$. hold the sheet there if it is magnetic.
$B$. hold the sheet there if it is non-magnetic.
$C$. move the sheet away from the pole with uniform velocity if it is conducting.
$D$. move the sheet away from the pole with uniform velocity if it is both,non-conducting and non-polar.
Choose the correct statement$(s)$ from the options given below:

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