An electric dipole with dipole moment $\vec{P}=(2.54 imes10^{-28}\...

Question

An electric dipole with dipole moment $\vec{P}=(2.54	imes10^{-28}\,	ext{C·m})(2.00\hat{i}+3.00\hat{j})$ is placed in an electric field $\vec{E}=\left(1000\,\dfrac{N}{C}ight)\hat{i}$. An external agent turns the dipole until its dipole moment is $\vec{P}=(2.54	imes10^{-28}\,	ext{C·m})(-3.00\hat{i}+2.00\hat{j})$. The work done by the agent is:

Accepted Answer

Potential energy of a dipole: $$U = -\vec{P}\cdot\vec{E}$$ Initial: $$U_i = -[(2.54	imes10^{-28})(2.00\hat{i}+3.00\hat{j})]\cdot(1000\hat{i}) = -(2.54	imes10^{-28})(2.00)(1000)$$ $$= -5.08	imes10^{-25}\ 	ext{J}$$ Final: $$U_f = -[(2.54	imes10^{-28})(-3.00\hat{i}+2.00\hat{j})]\cdot(1000\hat{i}) = -(2.54	imes10^{-28})(-3.00)(1000)$$ $$= +7.62	imes10^{-25}\ 	ext{J}$$ Work done by agent: $$W = U_f - U_i = 7.62	imes10^{-25} - (-5.08	imes10^{-25}) = 12.7	imes10^{-25} = 1.27	imes10^{-24}\ 	ext{J}$$ Hence the correct option is (B).

💬 Doubts & Comments

Abhi tak koi comment nahi

Apna comment likhein

💬 Doubts & Comments

Abhi tak koi comment nahi

Apna comment likhein

🔔 Email Updates Lein