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A magnetic needle has a frequency of 20 ...

A magnetic needle has a frequency of `20` oscillations per minute in the earth's horizontal field. When the field of a manget supports the earths horizontal field, the frequency increases to `30` oscillations per minute. The ration of the field of the magnet to that of the earth is

A

`4:7`

B

`7:4`

C

`5:4`

D

`4:5`

Text Solution

Verified by Experts

The correct Answer is:
C
`nalphasqrtBrArr(20)/(30)=sqrt(((H))/(B+B_(H)))rArrB=(5)/(4)B_(H)`
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NARAYNA-MAGNETISM-LEVEL-II(C.W)
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