IIT JEE , AIEEE Forum - Physics , Magnetism - AIEEE 2008 question(1) please give a detailed solution to it

rakesh61

A steel wire length L has Magnetic moment M is then bent in form of semicircle arc new magnetic moment will be

1] m 2] 2m/pi 3]m/l 4] ML

here pi = 3.14

i know answer is 2 but i want detailed solution

raman_shadow

length of wire = L

so circumference of semicircle = L
so radius of semicircle = L/pi
diameter = 2L/pi
as mag. moment

1/L

so m₁/m₂ = l₂/l₁
m₁/M = 2L/pi/L
m₁ = 2M/pi

cheers!

pls rate if crrect

krishna.gopal

Actually magnetic moment = pole strength*lengthh of magnel (l)
So when length becomes 2/pi times orignal length Mm becomes 2M/pi

raman_shadow

thnk u sir 4 crrecting my mistake.
let the wrong solution be still posted. it will help others to not fall into the trap i did