Question

A long cylindrical shell with a radius of 1cm has a charge uniformly distributed on its surface. If the magnitude of the electric field at a point 8cm radially outward from the axis of the shell is 85 N/C, how much charge is distributed on a 2m length of the charged cylindrical surface?

Answer 1

Answer: 756.25 *10^-12 C

Explanation: In order to explain this problem we have to consider that the electric field for large charged cylinder is given by:

E=λ/(2*π*εo*r) where λ is the charge per length. r is the distance to the cylinder centre.

then we have:

λ= E * 2*π*εo*r= 85*2*π*8.85*10^-12*0.08=378.12 C/m

for 2 meter long we have a total charge of:

Q=λ*L=378.12 C/m*2m=756.25 *10^-12 C