work done in moving a magnetic dipole from an angle ₁ to an angle ₂ w.r.t. the direction of magnetic field =

_{[1 ]}^{[2 ]} .d ... where is the torque reqd. to produce the given angular disp.

= _{[1 ]}^{[2 ]} M.B.sin.d

= - MB ( cos₂ - cos₁ )

= MB (cos₁ - cos₂ )

thus this work done is stored as the potential enrgy of the field-magnet system.

Thus .. U(₂) - U(₁) = MB (cos₁ - cos₂ )

Now in HCV .... it is written that let us assume that the potential energy at = 90^o as zero....and so the potential energy at an angle is

U() - U(90^o) = MB ( cos90^o - cos )

= - MBcos

Now why shuold we suddenly consider potential energy at = 90^o as zero ... ?????????

Amit Saxena , 11 Years ago

Grade upto college level