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Two circular rings A and B of radii nR a...

Two circular rings A and B of radii nR and R are made from the same wire. The Ml of A about an axis passing through the centre and perpendicular to the plane of A is 27 times that of the smaller loop B. What is the value of n if the length of A = n (length of B) ?

A

2

B

3

C

4

D

5

Text Solution

Verified by Experts

The correct Answer is:
B
For A, `R_(A)=nR," for "B, R_(B)=R`
`therefore" length of A = n (length of B)"`
Since the wires are of the same material
`therefore" Mass of A = n (mass of B)"`
`therefore I_(A)=m_(A)R_(A)^(2)=nm_(B)xx(nR)^(2)`
`=n^(3)m_(B)R^(2)=n^(3)I_(B)`
`therefore" "(I_(A))/(I_(B))=n^(3)=27" "therefore n=3`
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