All India Engineering / Architecture Entrance Examination (AIEEE)
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AIEEE 2007 Physics
Q. 30. A parallel plate condenser with a dielectric of dielectric constant K between the plates has a capacity C and is charged to a potential V volts. The dielectric slab is slowly removed from between the plates and then reinserted. The net work done by the system in this process is
- zero
Sol: No change in the energy of the system. Hence, not net work done by the system is zero. Correct choice: (4)
Q. 31. If 
are the accelerations due to gravity on the surfaces of the earth and the moon respectively and if Millikan’s oil drop experiment could be performed on the two surfaces, one will find the ratio 
- 1
- 0
Sol: Correct choice: (1)
Q. 32. A circular disc of radius R is removed from a bigger circular disc of radius 2R such that the circumferences of the discs coincide. The centre of mass of the new disc is 
from the centre of the bigger disc. The value of is 
Sol: If mass of circular disc is M, then mass of removed disc is
. Let centre of mass of remaining disc is at a distance x from centre, then
[In question x is given out to be . If we take that, then no choice is correct we believe in place of , it should be 
]
Correct choice: (1)