CBSE Class 12 Physics 2014 Delhi Set 3 Paper

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Question : 4
Total: 8
An electric dipole of length 2cm , when placed with its axis making an angle of 60 with a uniform electric field, experiences torque of 63Nm . Calculate the potential energy of the dipole, if it has a charge of ±2nC .
Solution:  
τ=pEsinθ
63=pEsinθ
pE
3
2
=63

So, pE=12
Potential energy of the dipole =pEcosθ
U=pEcos60
U=12×0.5
U=6J
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