CBSE Class 12 Physics 2014 Delhi Set 1 Paper

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Question : 16
Total: 30
An electric dipole of length 4cm, when placed with its axis making an angle of 60 with a uniform electric field, experiences a torque of 43Nm. Calculate the potential energy of the dipole, if its has charge ±8nC.
Solution:  

τ=pEsinθ
43=pEsinθ
pE
3
2
=43

So, pE=8
Potential energy of the dipole =pEcosθ
U=pEcos60
U=8×0.5
U=4J
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