Question

A bar magnet of length 12cm and pole strength 25 cgs is placed in magnetic meridian pointing with north pole towards geographical north. if the horizontal component of earth's magnetic field at the place be 0.3 cgs. Find out the position of neutral points.​

Answer 1

Answer:

When the north pole of magnet points towards geographical south, the neutral points lie on the axial line of the magnet.

Baxial=BHBaxial=BH

For a short magnet, we have

μ04π2Mr3=BHμ04π2Mr3=BH

here , r=30cm=0.3cm,BH=0.4G=0.4×10−4Tr=30cm=0.3cm,BH=0.4G=0.4×10-4T

⇒10−7×2M(0.3)2=0.4×10−4⇒10-7×2M(0.3)2=0.4×10-4

⇒M=0.4×10−4×(0.3)22×10−7⇒M=0.4×10-4×(0.3)22×10-7

=5.4Am2