CBSE Class 12 Physics 2014 Delhi Set 3 Paper

Question : 4 of 8

Marks: +1, -0

An electric dipole of length

2 {\cm}

, when placed with its axis making an angle of

60^{∘}

with a uniform electric field, experiences torque of

6 {√{3}} {\Nm}

. Calculate the potential energy of the dipole, if it has a charge of

± 2 n {\C}

Solution:

τ\;=p E sin \;θ

6 {√{3}}\;=p E sin \;θ

p E \;{{√{3}}}/{2}\;=6 {√{3}}

So,

p E=12

Potential energy of the dipole

=-p {\E} \cos θ

\;U=-p {\E} \cos 60^{∘}

\;U=-12 × 0.5

\;U=-6 {\J}

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