Calculate the potential difference between the two plates

Question

A disc of radius 10 cm carries a uniform surface charge density of 3.2 nC.m^-2. The electric field on the axis of the disc at a distance 15 cm form the disc is approximately

a) 283N.C-1

b)30.4N.C-1

c) 4263.3N.C-1

d) 2469.5N.C-1

2)A disc of radius 10 cm carries a uniform surface charge density of 10 micro coulomb per square meter. The electric field on the axis of the disc at a distance 0.1 cm form the disc is approximately

a) 3.8 x 107N.C-1

b)	2.8 x 105 N.C-1

c) 1.5 x 106 N.C-1

d)	5.6 x 105 N.C-1

3)Two flat charged conducting plates are parallel to each other and separated by a distance of 1 cm. One has a surface charge density of  2 nC.m^-2 and the other carries a surface charge density of  -2 nC.m^-2. What is the potential difference between the two plates?a)90Vb)15Vc)2.25Vd)11V