Electrostats doubt- Field just below a hemispherical surface

Isn't the disc electric field formula applicable for this q? Derived by using solid angle. Could someone show their working? I have a couple of doubts.

noriOP•5/1/25, 4:12 PM

ik this doesnt look like a hemisphere but i hope u get what i mean

iTeachChem Helper•5/1/25, 4:15 PM

@Gyro Gearloose

iTeachChem Helper•5/1/25, 4:15 PM

Note for OP

+solved @user1 @user2...

+solved @user1 @user2...

to close the thread when your doubt is solved. Mention the users who helped you solve the doubt. This will be added to their stats.

Nnori ik this doesnt look like a hemisphere but i hope u get what i mean

Opt•5/1/25, 4:17 PM

I'm guessing, but is it D?

noriOP•5/1/25, 4:22 PM

sorry no

Opt•5/1/25, 4:22 PM

Mb A

noriOP•5/1/25, 4:22 PM

i misread it mb

noriOP•5/1/25, 4:22 PM

nope i thought that too

noriOP•5/1/25, 4:22 PM

should i tell?

Opt•5/1/25, 4:22 PM

ok, then let me actually try

Opt•5/1/25, 4:23 PM

Idk why I even said D

Opt•5/1/25, 4:23 PM

A is the more likely one

noriOP•5/1/25, 4:23 PM

yeah cuz if it's close it acts like an infinite sheet

noriOP•5/1/25, 4:23 PM

but idk why that is not it

Nnori yeah cuz if it's close it acts like an infinite sheet

CorrodedCoffin•5/1/25, 4:23 PM

but A isnt correct right?

noriOP•5/1/25, 4:23 PM

nope

CorrodedCoffin•5/1/25, 4:23 PM

alrr

noriOP•5/1/25, 4:23 PM

at least acc to the key

CorrodedCoffin•5/1/25, 4:24 PM

key says C?

noriOP•5/1/25, 4:24 PM

yeah

CorrodedCoffin•5/1/25, 4:25 PM

damn

noriOP•5/1/25, 4:26 PM

if u use the disc wala formula you get the same exp except that it has a - sign and the ans has a + sign

noriOP•5/1/25, 4:26 PM

and im assuming the hemisphere doesnt have a base ie it's open

CorrodedCoffin•5/1/25, 4:26 PM

i was trying with gauss law but couldnt get much

CorrodedCoffin•5/1/25, 4:26 PM

ping me before closing if u get ans

noriOP•5/1/25, 4:26 PM

okay sure

OOpt A is the more likely one

Gamertug•5/1/25, 4:33 PM

i think its D too

Gamertug•5/1/25, 4:33 PM

by the sheet logic

Gamertug•5/1/25, 4:33 PM

there will be 2 sheets

noriOP•5/1/25, 4:37 PM

a better img i found online (same q)

noriOP•5/1/25, 4:38 PM

and i think the flat part is open

noriOP•5/1/25, 4:38 PM

the q doesnt explicitly mention anything like that

Nnori Isn't the disc electric field formula applicable for this q? Derived by using so...

who am i ?•5/1/25, 5:14 PM

who am i ?•5/1/25, 5:14 PM

integrate this from 0 to pi/2

Wwho am i ?Click to see attachment

CorrodedCoffin•5/1/25, 5:34 PM

gives D if my calc is correct

Wwho am i ?Click to see attachment

noriOP•5/1/25, 5:44 PM

isnt there smtg simpler than this? like maybe solid angles

CCorrodedCoffin gives D if my calc is correct

who am i ?•5/1/25, 5:52 PM

No it doesnt

who am i ?•5/1/25, 5:52 PM

I will send the calculation tomorrow i dont have a pen and its hard writing on laptop

Nnori isnt there smtg simpler than this? like maybe solid angles

who am i ?•5/1/25, 5:52 PM

Thats for discs right

who am i ?•5/1/25, 5:53 PM

these are rings

CorrodedCoffin•5/1/25, 6:30 PM

If this ain't correct imma kms

rn_image_picker_lib_temp_98b0e860-eea2-4345-85d9-1e1dc9194537.jpg

integralofe^2v•5/2/25, 12:51 AM

integralofe^2v•5/2/25, 12:51 AM

integralofe^2v•5/2/25, 12:57 AM

There might be just 1 error that maybe i took d exactly as zero and didnt use it as a limit so it might cause some issues

Nnori Isn't the disc electric field formula applicable for this q? Derived by using so...

SirLancelotDuLac•5/2/25, 1:43 AM

Ah I've seen this. This is painfully done using polar

SirLancelotDuLac•5/2/25, 1:43 AM

But yeah the answer is b for this case.

SirLancelotDuLac•5/2/25, 1:43 AM

c occurs for the case when the particle is at a distance R opposite to the center iirc.

SirLancelotDuLac•5/2/25, 1:58 AM

WhatsApp_Image_2025-05-02_at_07.27.59_bdabe269.jpg

Iintegralofe^2v There might be just 1 error that maybe i took d exactly as zero and didnt use it...

SirLancelotDuLac•5/2/25, 1:58 AM

This is the trickiest part in the question

SirLancelotDuLac•5/2/25, 1:59 AM

Because d is tending to zero, the field by the first ring (when theta is zero) is not zero, but sigma/2epsilon

Electrostats doubt- Field just below a hemispherical surface

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