Two metal plates having a potential difference of 800 V are 2 cm apart. It is found that a particle of mass 1 . 96 × 10 - 15 kg remains suspended in the region between the plates. The charge on the particle must be ( e = elementary charge)

Step-by-step solution

V = 800   V E = V d = 800 2 × 10 - 2   V   m - 1 = 4 × 10 4     V   m - 1 At equilibrium electrostatic force must be equal to force due to weight. q E = m g ⇒   q = m g E = 1 . 96 × 10 - 15 × 9 . 8 4 × 10 4 coulomb = 1 . 96 × 10 - 15 × 9 . 8 4 × 10 4 × 1 . 6 × 10 - 19 elementary charges = 3   e