A parallel plate capacitor is made of two circular plates separated by a distance of 5 mm

A parallel plate capacitor is made of two circular plates separated by a distance of 5 mm and with a dielectric of dielectric constant 2.2 between them. When the electric field in the dielectric is 3 × 104 V/m, the charge density of the positive plate will be close to

  1. 6 × 10–7 C/m2
  2. 6 × 104 C/m2
  3. 3 × 104 C/m2
  4. 3 × 10–7 C/m2

Answer

E = σ/Kεo

σ = EKεo 

Given:

E = 3 × 104 V/m

K = 2.2

εo = 8.85 x 10-12

Put the values of all quantities to get 

σ = 5.8 × 10-7  or 6 × 10-7 C/m2

The correct option is A.