An electric dipole with dipole moment 5 times 10^ -6 text Cm is aligned with a uniform electric field of magnitude 4 times 10^5 text N/C . The dipole is rotated through 60°. The change in potential energy is:

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NEET Physics QUESTION #1023

Question 1

An electric dipole with dipole moment \(5 \times 10^{-6}\ \text{Cm}\) is aligned with a uniform electric field of magnitude \(4 \times 10^5\ \text{N/C}\). The dipole is rotated through \(60°\). The change in potential energy is:

1.2 J
1.5 J
0.8 J
1.0 J✔️

Correct Answer Explanation

Initial PE: \(U_i = -pE\cos0° = -pE\). Final PE: \(U_f = -pE\cos60° = -\frac{pE}{2}\). Change: \(\Delta U = U_f - U_i = -\frac{pE}{2}+pE = \frac{pE}{2} = \frac{5\times10^{-6}\times4\times10^5}{2} = \frac{2}{2} = 1.0\ \text{J}\).

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