CBSE Class 12 Physics 2014 Delhi Set 2 Paper

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Question : 3
Total: 8
An electric dipole of length 2cm, when placed with its axis making an angle of 60 with a uniform electric field, experiences a torque of 83Nm. Calculate the potential energy of the dipole, if it has a charge of ±4nC.
Solution:  
τ=pEsinθ
83=pEsinθ
pE
3
2
=83

So, pE=16
Potential energy of the dipole
=pEcosθ
U=pEcos60
U=16×0.5
U=8J
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