The figure is a section of a conducting rod of radius R 1 = 1.60 mm and length L
ID: 1334285 • Letter: T
Question
The figure is a section of a conducting rod of radius R1 = 1.60 mm and length L = 12.30 m inside a thin-walled coaxial conducting cylindrical shell of radius R2 = 13.0R1 and the (same) length L. The net charge on the rod is Q1 = +3.50 × 10-12 C; that on the shell is Q2 = -2.12Q1. What are the (a) magnitude E and (b) direction (radially inward or outward) of the electric field at radial distance r = 2.09R2? What are (c) E and (d) the direction at r = 5.11R1? What is the charge on the (e) interior and (f) exterior surface of the shell?
I just need help with part a.
Explanation / Answer
a)
at r= 2.09 R2=2.09*13R1 = 2.09*13*1.6*106-3 m
It is outside 2 cylinder surfaces.
So E will be due to both Q1 and Q2
E= Q1/(2*pi*ebsoleneo*r*L) + Q2/(2*pi*ebsoleneo*r*L)
=((Q1+Q2)/(2*pi*ebsoleneo*r*L) )
=(3.5*10^-12 -2.12*3.5*10^-12) / (2*pi*8.854*10^-12 *(2.09*13*1.6*10^-3)*12.3)
= -0.132 N/C
Negative sign shows that it is directed inward
part c:
For calculating C you should note that
at r= 5.11 R1
It is between 2 cylinder surfaces.
So E will be due to only Q1
E= Q1/(2*pi*ebsoleneo*r*L)
I have solved part a for you