A magnetised steel wire is bent in the form of L . One arm of L is of length 4 cm and the other arm is of length 3cm . If the magnetic moment before bending is `p_(m)` , what will be the new magnetic moment ?

Explanation

Length of the steel wire before bending ,
l = 4+3 =7 cm
`therefore` pole -strength , `m=(p_(m))/(l)`
Distance between the two poles after bending ,
`l'=sqrt(4^(2)+3^(2))=5"cm"`
So , the new magnetic moment ,
`p'_(m)=m.l'=(p_(m))/(l).l'=(p_(m))/(7).5=0.714p_(m)`