## Saturday, January 12, 2013

### Torque on a Bar Magnet in a Magnetic Field

Let a bar magnet makes angle θ with magnetic field B and 2l be the length of the bar as show in figure.

Force on N-pole = mB along B and Force on S-pole = mB, opposite to B, since these are the equal and opposite forces they produce torque

ז = force x perpendicular distance. = mB x NA = mB x 2lsinθ therefore ז =MBsinθ

The direction of the torque is perpendicular to the the plain containing M and B, and given by right handed screw rules.

Magnetic dipole moment as the torque acting on a dipole held perpendicular to uniform magnetic field of unit strength

SI unit of M is JT-1

1. Force on N-pole = mB along B and Force on S-pole = mB, opposite to B..............But why these forces are in opposite directions?

1. Beacuse Megnetic bar contain two pole north and south

2. what is 'B'?

3. why force becomes equal to mB ?

4. Where does 2l goes in the last step?

5. Where does 2l goes in the last step?

1. Sir M=m×2L which is written correctly