Complex Flux

A hollow sphere of radius R R of uniform surface charge density σ \sigma , its center is placed at origin A A .

A hollow hemispherical surface of R R is at centre B B ( x 2 ) 2 + y 2 + z 2 = 1 , x 2 (x-2) ^{2}+y^{2}+z^{2}=1,x≥2

Find the electric flux through the curved surface of that hemisphere due to that hollow uniformly charged sphere.

Details and Assumptions
1) R = 1 R=1
2) Coordinates of A A and B B are ( 0 , 0 , 0 (0,0,0 and ( 2 , 0 , 0 ) (2,0,0) respectively.
3) σ = 1 \sigma=1
4) Electric permittivity ϵ 0 = 1 \epsilon_{0}=1
5) I have provided a two dimensional figure. But this system is in three dimensions. I have provided the view of figure from Y -Y axis.
6) The answer is positive.

This problem is original.

This problem is dedicated to my respected teacher Steven Chase


The answer is 0.6633.

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2 solutions

Steven Chase
Jul 30, 2020

Nice one. Commented solution code is attached. I moved the source charge to ( 0 , 0 , 2 ) (0,0,-2) and made the half sphere sit at the origin.

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import math

Num = 10000   # spatial resolution parameter

R = 1.0   # sphere radius
A = 4.0*math.pi*(R**2.0)  # sphere surface area
sigma = 1.0  # charge density
e0 = 1.0  # permittivity

x0 = 0.0   # coordinates of source charge
y0 = 0.0
z0 = -2.0

#############################################

Q = A*sigma   # source charge value
k = 1.0/(4.0*math.pi*e0)  # Coulomb constant

#############################################

dtheta = 2.0*math.pi/Num   # angle increments
dphi = (math.pi/2.0)/Num   # spherical coordinates

F = 0.0   # initialize flux to zero

phi = 0.0  

while phi <= math.pi/2.0:  # integrate over target sphere surface

    theta = 0.0

    while theta <= 2.0*math.pi:

        x = R*math.cos(theta)*math.sin(phi)  # xyz coordinates of surface point
        y = R*math.sin(theta)*math.sin(phi)
        z = R*math.cos(phi)

        nx = x/R  # surface normal vector
        ny = y/R
        nz = z/R

        dS = (R**2.0)*math.sin(phi) * dtheta * dphi  # surface area patch

        dSx = dS*nx  # surface area vector
        dSy = dS*ny
        dSz = dS*nz

        Dx = x - x0  # diplacement vector from source charge to surface
        Dy = y - y0
        Dz = z - z0

        D = math.sqrt(Dx**2.0 + Dy**2.0 + Dz**2.0)  # distance from source charge to surface

        ux = Dx/D  # unit vector corresponding to D vector
        uy = Dy/D
        uz = Dz/D

        E = k*Q/(D**2.0)  # electric field magnitude

        Ex = E*ux  # electric field vector
        Ey = E*uy
        Ez = E*uz

        dF = Ex*dSx + Ey*dSy + Ez*dSz  # infinitesimal flux contribution

        F = F + dF  # accumulate flux

        theta = theta + dtheta

    phi = phi + dphi

#############################################

# Print results

print Num
print F

#>>> 
#1000
#0.664438443152
#>>> ================================ RESTART ================================
#>>> 
#2000
#0.66388593149
#>>> ================================ RESTART ================================
#>>> 
#4000
#0.663609714095
#>>>
#>>> 
#10000
#0.663289381756
#>>> 

Amazing! Yeah; the integral Neeraj asked me to solve must have been the wrong one to solve the problem. That's what I thought. A nice numerical solution, sir. I love how numerical methods are so straightforward and dependable upon.

Krishna Karthik - 10 months, 2 weeks ago

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Thanks. Yeah, the thing I love most about code is that I don't have to bother with big complicated expressions. I can assemble things in small pieces.

Steven Chase - 10 months, 2 weeks ago

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Yes, indeed. I don't enjoy simplifying huge expressions. Did you see how big that integral Neeraj came up with was? Biggest thing I've seen in my life lol. Much easier to do numerically.

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik No matter which method is good and whatever the expression is, the main thing is that Steven Chase is a stud and smart guy.

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley Lmao. Well, you have a long way to go. Steven Chase is more than twice as old as you, and I am younger than all of you lol, so boy, I have a long way to go.

I literally just started learning physics and maths and shit 3-4 years ago. I have a lot to do.

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik I have started learning physics just 2 years ago.
And Steven Chase is a smart guy.

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley Yeah. I started learning advanced math around three years ago, and physics only 1.5 years ago.

Krishna Karthik - 10 months, 2 weeks ago

@Talulah Riley I think I started learning physics back in 2003

Steven Chase - 10 months, 2 weeks ago

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@Steven Chase Ok, boomer.

Nah jk jk jk jk. Just kidding lmao

Krishna Karthik - 10 months, 2 weeks ago

@Steven Chase I was born 2 years after 2003🤣

Krishna Karthik - 10 months, 2 weeks ago

@Steven Chase Just wanna know: did you do any physics in High School or anything mathematics related in high school?

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik I took math and physics classes, but didn't do any competitions or anything

Steven Chase - 10 months, 2 weeks ago

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@Steven Chase Ah, fair enough. Competitions aren't really worth it in my opinion. Most of the people who win them are just Asians.

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik @Steven Chase ,so let's end this discussion with a sentence.
"mention[1247521:Steven Chase] is a smart guy".

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley Anyways, I have to go for something lol. See ya!

Krishna Karthik - 10 months, 2 weeks ago

@Steven Chase @Steven Chase Do you teach students?
I want to study in your class.

Talulah Riley - 10 months, 2 weeks ago

@Steven Chase @Steven Chase 16 May 2003 is my date of birth.when I was born you started learning physics. Nice.

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley Hehe that's funny.

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik what is your date of birth?

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley bruh 2005. Can't tell you the month and the day tho, soz

Krishna Karthik - 10 months, 2 weeks ago

@Talulah Riley Physics is kinda new to me; I started programming around 2 years ago.

Krishna Karthik - 10 months, 2 weeks ago

@Steven Chase Very nice solution.
You are a very smart and intelligent guy.

Talulah Riley - 10 months, 2 weeks ago

@Steven Chase Do you know who is Lil Dougy ?? In the below link it is written your name also. https://www.facebook.com/SchweitzerEngineering/posts/sel-lead-research-engineer-doug-taylor-has-been-selected-to-participate-in-the-n/2205749516118795/
By the way @Krishna Karthik share your views

Talulah Riley - 10 months, 2 weeks ago

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Yeah; Dougy looks like a subordinate, from what I understand. He likes to help all the new engineers. Cheers for little Dougy! Good on ya, mate!

Krishna Karthik - 10 months, 2 weeks ago

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@Steven Chase @Krishna Karthik like wise he has also helped us
We are also engineers. mention[1247521:Steven Chase] is really a very smart man.
Yeah bro,Lil Dougy is also amazing.

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley Good on ya, Dougo mate!

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik yeah bro, that good bro
Dougy is amazing and good one.
Steven Chase is also a very smart guy. Lol

Talulah Riley - 10 months, 2 weeks ago

Yeah, Doug is indeed a good guy

Steven Chase - 10 months, 2 weeks ago

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@Steven Chase Lmao🤣 "Lil Dougo"

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik why are you laughing so much???

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley Just "Dougo" Idk... I just found that so funny

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik because that relates with Dog word .
Be we have to respect them instead of laughing.
Thierr knowledge is very far from you and me.

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley True, true. And Aussies just add "o" to any name to make a nickname.

Krishna Karthik - 10 months, 2 weeks ago

@Steven Chase @Steven Chase you are also a v e r y v e r y very^{very} good guy.
Is that photo of you or Lil Dougy?

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley @Steven Chase @Neeraj Anand Badgujar Yeah; I also kinda want to know.

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik by the way the photo of that man seems me sexy also.
Share you views bro.?

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley What? Are you gay? I didn't think you were gay.

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik I am not a gay.
Why are you saying this???

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley 'cause you said that photo of the man seems "sexy" Sorry if I misunderstood lol... I maybe took that in the wrong sense of "sexy". I kinda misunderstood when you said "sexy". lol

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik but the epic question is that he is Steven chase or Lil Douga

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley Diggity Dougo. I bet he's doug.

Krishna Karthik - 10 months, 2 weeks ago

Did you just change your name to Lil Doug ?????? Bro, you're a MADLAD!!!!!

What an absolute lad. You did it for the lads!!!!!

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik I can do anything bro.

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley What an absolute bloke. A true madlad.

Krishna Karthik - 10 months, 2 weeks ago

@Krishna Karthik what does lads mean?

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley Just look it up on Urban Dictionary or something. It means a guy that's willing to do anything for the group.

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik yeah bro, I want real friends, not fake friends.

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley @Krishna Karthik so I am now Lil Dougy, talk with me in a very respective manner.
Ok

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley Sir, what do you want me to do to improve the SEL-400 series? What do you say, boss?

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik yeah as a entrepreneur in SEL, I am improving my company to gain more profits.

Talulah Riley - 10 months, 2 weeks ago

@Talulah Riley Nah, jkjk, madlad's just an internet term. Anyways, gtg.

Krishna Karthik - 10 months, 2 weeks ago

@Krishna Karthik check my profile status..

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley @Krishna Karthik you have deleted you last message.

Talulah Riley - 10 months, 2 weeks ago

@Krishna Karthik I am in US .
I am going to bed now. It is night here.
Good night.

Talulah Riley - 10 months, 2 weeks ago

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XD Alright; I'm going to work a little bit overtime; going to keep you posted when I've fixed the issue with the capacitor system.

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik what capacitor??

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley Bro I'm just roleplaying. SEL is an electrical engineering company.

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik I have to sleep bit early because tomorrow is my meeting in SEL company and @Steven Chase is also in meeting. So bye tomorrow we will meet in meeting.

Talulah Riley - 10 months, 2 weeks ago

@Talulah Riley Goodnight boss.

Krishna Karthik - 10 months, 2 weeks ago

@Krishna Karthik we are missing Steven chase in role playing.

Talulah Riley - 10 months, 2 weeks ago

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Yeah, ikr? I lost it when he said "Doug is indeed a good guy"

Here's some good words about Doug from him:

“Doug has made important contributions to many of SEL’s recent technological advances, has served as a mentor to many new engineers, and is a highly regarded member of our development group. His professionalism and technical expertise make him an excellent SEL representative for this symposium"

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik Yeah bro.He said he is a very good guy. I think he is friend of Steven Chase.
Now I am going to bed.

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley Alright, see you bud. I just realised I have to practice my piano; totally forgot lol.

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik Do you play piano? By the way, I like singing very very much.
Do you also like?

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley I don't like singing that much; I'm kinda bad at singing lol. Look at my "About section". Scroll down. You'll see that I do play the piano :)

Krishna Karthik - 10 months, 2 weeks ago

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@Krishna Karthik @Krishna Karthik which piano you have? What is it's price?

Talulah Riley - 10 months, 2 weeks ago

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@Talulah Riley I don't have a grand piano or anything like that, but I have a second hand upright (new). It's a good model; Bechstein. It only cost me around 10,000 AUD. The owner wanted to give it up so bad lol. That's such a good price for a Bechstein piano. Crazy, isn't it?

Anyway, yea, I saved up to buy it. So happy when I got it :)

Krishna Karthik - 10 months, 2 weeks ago

@Talulah Riley I mainly play classical composers like Chopin, Beethoven, Mozart, Bach, etc.

Krishna Karthik - 10 months, 2 weeks ago

@Steven Chase Please help me in this problem
If it is getting hard analytically, assume some values with your own and solve with python.
Thanks in advance.

Talulah Riley - 9 months ago

Sorry for typos:

@Novak Radivojević Thanks for the solution.
I didn't understand how can we replace the sphere with point charge, can you elaborate more?
Thanks in advance.

Talulah Riley - 10 months, 2 weeks ago

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Hi, charged hemisphere and its equivalent point charge generate the same electric field vector over the spherical cap. Calculating flux in both cases would give the same result. I just felt that solving the problem this way would be nicer.

Novak Radivojević - 10 months, 2 weeks ago

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@Novak Radivojević But on what basis or proof we can say that point charge and spherical sphere can be treated same. ? I am very curious about you method.
Thanks in advance.

Talulah Riley - 10 months, 2 weeks ago

@Novak Radivojević hey bro till now, I am not able to understand you solution?

Talulah Riley - 9 months, 1 week ago

@Novak Radivojević How can we replace sphere with point charge??

Talulah Riley - 9 months, 1 week ago

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Hey, sorry for ghosting you about this problem, it's just that both the sphere and the point charge generate the same electric field, and thus the same flux at points that are outside of the sphere. Electric field for both can be calculated as E = Q 4 π ϵ 0 r 2 E = \dfrac{Q}{4\pi\epsilon_{0}r^2} , where r > R r > R .

Novak Radivojević - 9 months, 1 week ago

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@Novak Radivojević but how did you know that???

Talulah Riley - 9 months, 1 week ago

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@Talulah Riley Well, formula for electric field of a point charge is known to be the one I mentioned in the previous comment. Formula for E field around a sphere can be derived by applying Gauss' Law, and after that you'll just get the same formula for point charge. I just skipped the part with Gauss' Law.

Novak Radivojević - 9 months, 1 week ago

@Novak Radivojević Did you deleted you comment?

Talulah Riley - 9 months, 1 week ago

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