Given, mass, m=30.7×10−6kg Charge, q=2×10−8C Electric field, E=2×104V∕m Let T is the tension in the string and θ is angle of string with vertical. In equilibrium, T‌sin‌θ=qE ........(i) T‌cos‌θ=mg ........(ii) From Eqs. (i) and (ii), we get tan‌θ=