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  • A bar magnet of magnetic moment m is placed along the magnetic meridian. If the earth's magnetic field is B, the work required to turn the magnet through an angle <img alt="\theta" src="ht

A bar magnet of magnetic moment m is placed along the magnetic meridian. If the earth's magnetic field is B, the work required to turn the magnet through an angle \theta  is
 

Option: 1

\mathrm{m B \sin \theta }


Option: 2

\mathrm{m B \cos \theta }


Option: 3

\mathrm{m B(1-\cos \theta) }


Option: 4

\mathrm{m B(1+\cos \theta)}


Answers (1)

best_answer

If a torque\tau  is applied, the work done is

\mathrm{W =\int_0^\theta \tau d \theta=\int_0^\theta m B \sin \theta d \theta \\ }

\mathrm{ =-m B|\cos \theta|_0^\theta \\ }

\mathrm{ =-m B(\cos \theta-1)=m B(1-\cos \theta) }

Hence the correct choice is (c).

Posted by

Ritika Harsh

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