Question

An electric dipole consists of two unlike charges of magnitude 2 × 10⁻⁶ C each and separated by 4 cm. The dipole is placed in an external electric field of 10⁵ N/C. Calculate the work done by an external agent to turn the dipole through 180°.

Answer 1

Given: q = 2 × 10⁻⁶ C

2l = 4 cm = 4 × 10⁻² m

E = 10⁵ N/C

θ₁ = 0°

θ₂ = 180°

p = q × 2l

= 2 × 10⁻⁶ × 4 × 10⁻²

= 8 × 10⁻⁸ Cm

Now, W = pE (cos θ₁ − cos θ₂)

= 8 × 10⁻⁸ × 10⁵ × (cos 0° − cos 180°)

= 1.6 × 10⁻² J