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Question
An electric dipole of length 4 cm, when placed with its axis making an angle of 60° with a uniform electric field, experiences a torque of `4sqrt3`Nm. Calculate the potential energy of the dipole, if it has charge ±8 nC
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Solution
Torque, τ=PEsinθ=(Ql)Esinθ ...(1)
Here, l is the length of the dipole, Q is the charge and E is the electric field.
Potential energy, U=−PEcosθ=−(Ql)Ecosθ ...(2)
Dividing (2) by (1):
`T/U=((Ql)Esintheta)/(-(Ql)Ecostheta)=-tantheta`
`=>U=-T/(tantheta)`
`=>U=-T/(tan60^@)`
`=>U=(-4sqrt3)/sqrt3`
⇒U=−4 J
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