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Let r be the distance of a point on the ...

Let `r` be the distance of a point on the axis of a magnetic dipole from its centre. The magnetic field at such a point is proportional to

A

1/r

B

1/r2

C

1/r3

D

NOT

Text Solution

Verified by Experts

The correct Answer is:
B
The coercivity of bar magnet `4xx10^(3)A-m^(-1)` Length of solenoid=12cm, Number of turns=60
The coercivity of 12cm length of solenoid
`" " 4xx10^(3)xx12xx10^(-2)=480`
Now, current through each turn to demagnetise =`(480)/(60)=8A`
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