Write the expression for the work done on an electric dipole of dipole moment \overrightarrow{p} in turning it from its position of stable equilibrium to a position of unstable equilibrium in a uniform electric field { {\E}}^{\to}.

CBSE Class 12 Physics 2013 Paper - Question 1

Question : 1 of 29

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Write the expression for the work done on an electric dipole of dipole moment

{p}↖{→}

in turning it from its position of stable equilibrium to a position of unstable equilibrium in a uniform electric field

{ {\E}}↖{→}

Solution:

In stable equilibrium the angle between

{P}↖{→}

and

{E}↖{→}

0^{∘}

In unstable equilibrium the angle between

{P}↖{→}

and

{E}↖{→}

180^{∘}

\;\text " So, "\; \;\;

\;\text " the work done "\;\;=P E (\cos θ_1-\cos θ_2)

=P E (\cos 0^{∘}-\cos 180^{∘})

\;=P E(1+1)

\;=2 P E

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