Test Index

CBSE Class 12 Physics 2013 Paper

© examsnet.com
Question : 1 of 29
Marks: +1, -0
Write the expression for the work done on an electric dipole of dipole moment p⃗\vec{p} in turning it from its position of stable equilibrium to a position of unstable equilibrium in a uniform electric field E⃗\vec{E}.
Solution:  
In stable equilibrium the angle between P⃗\vec{P} and E⃗\vec{E} is 0∘0^{\circ}
In unstable equilibrium the angle between P⃗\vec{P} and E⃗\vec{E} is 180∘180^{\circ}
   So,       \;\text{ So, }\; \;\;    the work done     =PE(cos⁡θ1−cos⁡θ2)\;\text{ the work done }\;\;=P E (\cos \theta_1-\cos \theta_2)
=PE(cos⁡0∘−cos⁡180∘)=P E (\cos 0^{\circ}-\cos 180^{\circ})
  =PE(1+1)\;=P E(1+1)
  =2PE\;=2 P E
© examsnet.com
Go to Question:
Next Question