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. `I gt IIIgt II gt IV`
B. `I gt II gt III gt IV`
C. `I gt IV gt II gt III`
D. `III gt IV gt I gt II`

Answer

C

Explanation

(i) `U = - MB cos theta`
`U_("max") = MB`
As `theta = 180^@`
(ii) as `vecM bot vecB`
`U=0`
(iii) `theta rarr` acute `(lt 90^@)`
`U =- MB cos theta`
`U lt 0`
(iv) `theta rarr` obtuse
`(theta gt 90^@)`
`U =-vecMBcos theta`
`U gt0`
`implies (i) gt (iv) gt (ii) gt (iii)`