A current carrying loop is placed in a uniform magnetic field in four different orientations I, II, III and IV, arrange them in the decreasing order of potential energy. (I) (II) (III) (IV)

Question

A current carrying loop is placed in a uniform magnetic field in four different orientations I, II, III and IV, arrange them in the decreasing order of potential energy. (I) (II) (III) (IV), $ \mathrm{I}>\mathrm{III}>\mathrm{II}>\mathrm{IV} $, $ \mathrm{I}>\mathrm{II}>\mathrm{III}>\mathrm{IV} $, $ \mathrm{I}>\mathrm{IV}>\mathrm{II}>\mathrm{III} $, $ \mathrm{III}>\mathrm{IV}>\mathrm{I}>\mathrm{II} $

MARKS App · Accepted Answer

We know potential energy of a magnetic dipole in external magnetic field B → is U = - M → . B → = - M B cos θ where M → is magnetic moment of the loop, and θ is angle between M → and B → . We can see that U is maximum when θ = 180 ° and minimum when θ = 0 ° . So, as θ decreases from 180 ° to 0 ° , potential energy also decreases.

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