capacitance
how to approach this q? i found charges on each capacitor but which charge do we use for finding the capacitance
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@Gyro Gearloose
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Cylindrical capacitor formula works here ig.
but how to do it
I got a different answer for some reason
I tried converting to equivalent circuit.
There are 3 capacitors out of which AB and BC are shorted so consider CD and D and infinity as capacitors in parallel
Oh I forgot D and infinity
Ah no I think I messed up...
im getting option a
We would consider this right? Because I'm getting the answer as nota for some reason.
I got 8/7 πϵa
Considering CD and D-∞, there is 48πϵa and 16πϵa in parallel so 64πϵa maybe?
I think I need to revise this :sweaty:
just a side point that's been tripping me up about this question but
my teacher told me that charge induction only happens from the inside shell to the outside shell?
Yeah, because the net charge inside closed conducting surface must be zero.
so that means shells C, B and A can't acquire a charge?
and thus can't acquire a capacitance?
i suck at this chapter bro
No they could acquire charge, the potential would be 0 at earthed places.
oh charge flow is simply because of pot diff
Yep.
Is this not the equivalent circuit?
Ye. AB,BC are shorted so its just combination of two parallel capacitors?
Oh I think I did calc errors but still Im getting A.
Ok, I got B
But my method was stupid to the extreme.
Or maybe the question was intended to confuse. Idk
Basically, the primary rule that governs charge distribution on conducting shells is that the field inside the shell must be zero. And it is already zero because the charge is uniformly distributed on D. Whatever in inside, is utterly useless. There is no need for a charge to be induced on any of the inner shells. So the only capacitance is between D and ∞
*net field
There is field on the inside tho right? (Like C is at 0V and D is at some other voltage so field exists b/w C and D)
i think the answer should be a tho
Gauss' Law says no field.
Is it wrong to say there is field between inner surface of D and outer sirface of C?
There isn't any charge on the inner surface of D though?
It's on the outer surface
Ah I see.