CBSE Class 12 Physics 2013 Paper

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Question : 1
Total: 29
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
is 0
In unstable equilibrium the angle between
P
and
E
is 180
So, the work done =PE(cosθ1cosθ2)
=PE(cos0cos180)
=PE(1+1)
=2PE
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