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A steel wire of length l has a magnetic ...

A steel wire of length l has a magnetic moment M. It is then bent into a semicircular arc. The new magnetic moment is

A

M

B

`(2M)/(pi)`

C

`(M)/(l)`

D

`Mxxl`

Text Solution

Verified by Experts

The correct Answer is:
B
Magnetic moment of a wire of length l is
M = ml

where m is the strength of each pole,
When the wire is bent into a semicircle of radius r, then
`l pi r or r = l /pi`
Now, the distance between two poles
`= 2 r = (2l)/(pi)`
Its new magnetic moment is
`M. = m xx 2r = m xx (2l)/(pi) = (2)/(pi) (m xxl ) = (2M)/(pi)`
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