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Directions (Q. No. 6 to 10):

Read the following text and answer the following  An questions on the basis of the same:

Electromagnetic damping: Take two hollow thin cylindrical pipes of equal internal diameters made of aluminium and PVC, respectively. Fix them vertically with clamps on retort stands. Take a small cylindrical magnet having diameter slightly smaller   than the inner diameter of the pipes and drop it through each pipe in such a way that the magnet does not touch the sides of the pipes during its fall.

You will observe that the magnet dropped through the PVC pipe takes the same time to come out of the pipe as it would take when dropped through the same height without the pipe.

Now instead of PVC pipe use an aluminium pipe.

Note the time it takes to come out of the pipe in each case. You will see that the magnet takes much longer time in the case of aluminium pipe.

Why is it so ? It is due to the eddy currents that are generated in the aluminium pipe which oppose the change in magnetic flux, i.e., the motion of tlie magnet. The retarding force due to the eddy currents inhibits the motion of the magnet. Such phenomena are referred to as electromagnetic damping.

Note that eddy currents are not generated in PVC pipe as its material is an insulator whereas aluminium is a conductor.

This effect was discovered by physicist Foucault (1819-1868).

Eddy current is generated in a:

A) metallic pipe.

B) PVC pipe.

C) glass pipe.

D) wooden pipe.