An electric dipole is made up of 2 particles having charges1micro columbmass 1 kgand other withcharge _1 microcolumbmass 1 kg separated by distance 1m it is in equilibriumin a uniformelectricfield of 20×1000 volt per metre of dipole is deflectedthroughan angle 2 degreetime taken by it to come again in equilibriumis

Torque =(I × α) ...1 ( alpha = acceleration ) And also Torque = PEsin θ .....2From 1 and 2 I ×α = PEsinθ. We know( I = mr^2 ) Here there are 2 bodies And r = L/2 Then I = 2×m×(L/2)^2 =(mL^2)/2 And α =( w^2) ×θ(mL^2)/2. ×(w^2)×θ = -q×E×L×θ. (Sinθ~θ.)W^2 =( -2qE/mL)W= √(2qE/mL)Time period = 2π/w = 2π×1/w = 2π√(mL/2qE)Dipole takes T/4 of time to come again equilibrium. t =(2π/4)√(mL/2qE)Subtituting values t =( π/2)√(1×1)/(2×10^-6 ×20×10^3) t = (π/2)×5 t.= 2.5π sec . Answer