A current carrying loop is placed in a uniform magnetic field in four different orientations , I,ii,iii & iv arrange them in the decreasing order of potential Energy`

Options

A. `IgtIIIgtIIgtIV`
B. `IgtIIgtIIIgtIV`
C. `IgtIVgtIIgtIII`
D. `IIIgtIVgtIIgtI`

Answer

A

Explanation

`U=-vec(M).vec(B)=-MB cos theta`
In case I, `theta=180^(@).U=+MB`
In case `II,theta=90^(@).U=0`
In case `III, theta =` acute`.U=+ve(` less then `+MB)`
In case `IV, " "theta =` obtuse`U=-ve" ",`
`:. IgtIIIgtIIgtIV`.