Practice question

Given: A dipole p = 7 × 10⁻⁹C m is rotated from θ = 90° to 0° in a field E = 2 × 10⁵N/C . What is the work done? These values define the system as per NCERT data. Formula: Work done: W = p E (cos θ_0 - cos θ_1) = 7 × 10⁻⁹ × 2 × 10⁵ × (cos 90° - cos 0°). This is standard NCERT relation. Substitution & Calculation: W = 7 × 10⁻⁹ × 2 × 10⁵ × (0 - 1) = -1.4 × 10⁻³J . Result: The computed value matches expected outcome and confirms correct choice as per NCERT.