Register to reply

Electric flow

by ori
Tags: electric, flow
Share this thread:
ori
#1
Oct30-04, 03:19 PM
P: 30
http://t2.technion.ac.il/~snoop/Q.gif
Q is at one point
R is the radius of this cylinder, it's height is 2h
the cylinder is without the bases.
how can i calculate the electric flow through it?
the final answer is Q/[epsilon0*sqrt(1+R^2/h^2)]
Phys.Org News Partner Science news on Phys.org
Hoverbike drone project for air transport takes off
Earlier Stone Age artifacts found in Northern Cape of South Africa
Study reveals new characteristics of complex oxide surfaces
Tide
#2
Oct30-04, 03:30 PM
Sci Advisor
HW Helper
P: 3,146
Why don't you try calculating the flux through the flat top and bottom of the cylinder? Then you could subtract it from the total flux given by Gauss' Law.
ori
#3
Oct30-04, 03:38 PM
P: 30
Quote Quote by ori
http://t2.technion.ac.il/~snoop/Q.gif
Q is at one point
R is the radius of this cylinder, it's height is 2h
the cylinder is without the bases.
how can i calculate the electric flow through it?
the final answer is Q/[epsilon0*sqrt(1+R^2/h^2)]
where is my mistake:

we take ball with radius sqrt(R^2+h^2) and look on the rounded bases: the area of this ball inside the cylinder.

flow through bases / flow through all ball = bases area / all ball area

gaus: all ball flow is Q/epsilon0

all ball area is 4pi(R^2+h^2)

base area = circumference of projection of the base on y=2h * height of base
=(2pi*R)*[sqrt(R^2+h^2)-h]

2 bases area = base area * 2 = 4pi*R[sqrt(R^2+h^2)-h]

flow through bases=bases area*flow through all ball / all ball area=
= 4pi(R^2+h^2)Q/(epsilon0 4pi*R[sqrt(R^2+h^2)-h])=
Q(R^2+h^2)/(epsilon0 *R[sqrt(R^2+h^2)-h])

now that's not like that right answer, coz we can assign r=1 h=1
my answer qives 2/(sqrt(2)-1) * Q/epsilon0 = 2(1+sqrt(2)) * Q/epsilon0
right answer gives 1/sqrt(2) * Q/epsilon0

ori
#4
Oct30-04, 03:39 PM
P: 30
Electric flow

Quote Quote by Tide
Why don't you try calculating the flux through the flat top and bottom of the cylinder? Then you could subtract it from the total flux given by Gauss' Law.
we get too hard integral at that case:
S r^2/(r^2+h^2)^(3/2) dr
or something like that


Register to reply

Related Discussions
Period of an electric dipole rotating in an external electric field Introductory Physics Homework 2
Transition from pipe flow to open channel flow Mechanical Engineering 6
Can an inviscid flow rotational? Potential Flow? Mechanical Engineering 2
Temp flow and electrical flow Classical Physics 5
Electric Flow Classical Physics 36