The particle P shown in the figure has a mass of 10 kg and a charge of  -0.01  μC. Each plate has a surface area 10-2m2 on one side. What potential difference V should be applied to the combination to hold the particle P in equilibrium?

Electrical force is balanced by the weight of the massmg=E,  where  E=electric  fieldor mg=qVdwhere  d=separation  at  the  platesε0Ad=C⇒1d=Cε0Aor V=2mgε0AqC=10-6×2.2×10-12×10-210-5×4×10-8=10-6×9.8×8.88×10-12×100×10-410-8×0.04×10-6= 43 mV