Posted by **Monica** on Thursday, September 1, 2011 at 6:04pm.

Consider a disk of radius 2.6 cm with a uniformly distributed charge of +3.6 µC. Compute the magnitude of the electric ﬁeld at a point on the axis and 3.3 mm from the center. The value of the Coulomb constant is 8.98755 × 10^9 Nm2/C2.

Answer in units of N/C

Compute the ﬁeld from the near-ﬁeld approximation x ≪ R .

Answer in units of N/C

Compute the electric ﬁeld at a point on the axis and 31 cm from the center of the disk.

Answer in units of N/C

Approximate the ﬁeld by treating the disk as a +3.6 µC point charge at a distance of 31 cm.

Answer in units of N/C

This is what I know so far:

E=F/q=kQ/r^2

I started with E=(8.98755*10^-6)/(.0033 m)^2

E=2.97*10^9 N/C

I feel like I am missing a step. I know I use this idea though.

HELP! Thanks!