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Two short magnets have equal pole streng...

Two short magnets have equal pole strength but one is twice as long as the other. The shorter magnet is placed at 20 cm in tan A position from the compass needle. The longer magnet must be placed on the other side of the magnetometer for no defiection at a distacne equal to

A

30 cm

B

`30 xx (2)^(2//3) cm `

C

`30 xx (2)^(1//2) cm `

D

`30 xx 2 cm `

Text Solution

Verified by Experts

The correct Answer is:
C
For magnets to have equal and opposite filed at the compass needle.
`(mu_(0))/(4pi) (2M)/(d^(3)) = (mu_(0))/(4pi) (M)/((30)^(3))`
or `d^(3) = 2 xx (30)^(2)` .
or `d = (2^(1//3)) xx 30 cm`
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