You may have a valid point, I don't know. Here is the first response, but beware it does not copy and paste properly. ....
What is the resistance of an RC circuit if it charges an 88uf capacitor from 336V to 710V in 2 minutes 17 seconds?
ChatGPT
The charging of a capacitor in an RC circuit follows an exponential curve given by the formula:
https://www.electronics-tutorials.ws/rc/rc_1.html
I'll sub an image of the formula from the web (below), with the following variable assignments:
Where:
Vc is the voltage across the capacitor
Vs is the supply voltage
e is an irrational number presented by Euler as: 2.7182
t is the elapsed time since the application of the supply voltage
RC is the time constant of the RC charging circuit
- V(t) is the voltage across the capacitor at time tt, [Vc in image formula]
- V0 is the initial voltage across the capacitor, [Vs in image formula]
- R is the resistance in ohms,
- C is the capacitance in farads,
- t is the time in seconds,
- e is the base of the natural logarithm.
[some clean up]
... capacitor charges from 336V to 710V in 2 minutes and 17 seconds, which is ... 137 seconds. The initial voltage V0 is 336V, the final voltage V(t)V(t) is 710V, and the time tt is 137 seconds.
Now, let's rearrange the formula to solve for the resistance RR:
R=−tC⋅ln(V0−V(t)V0)
Plug in the values:
R=−137(88×10−6)⋅ln(336−710336)
R≈1.37×106 Ω
Therefore, the resistance of the RC circuit is approximately 1.37 MΩ.
¯\_(ツ)_/¯
I dunno what it did exactly, can you get a screenshot of the formulas?
Oddly, One Time Constant (R*C) is 120.56 seconds, close, but *not* 137 seconds.
I plugged that formula into a spreadsheet, and I can't get a match to their answer. I think it has mashed up the application of "Supply Voltage" with 'starting voltage' in the question.
But what I did find is if I assume 710 as the supply voltage, it would take just 77.3 seconds to charge to 336V, so that doesn't seem to be what it did. Hmmm, too much coincidence between 137 seconds, and 1.37 MOhm?
At any rate, I say the way the question is worded makes it undefined. So I'm not sure what ChatGPT was 'thinking'.
It probably made the same mistake humans make - plug some numbers into a formula that seems right, get an answer that seems reasonable on the surface, so go with it! But what did it do?
Again, if you can get a screenshot of the formula, that would help. Also, try asking the question differently, like:
" What is the resistance of an RC circuit if it charges an 88uf capacitor from 336V to 710V in 2 minutes 17 seconds
from a 1000V source?"
I'm simple minded, so I would look at only the voltage deltas (subtract 336 from all), charging from 336 to 710 with a 1000V source is the same as charging from 0 to 374V from a 664V source. For that, I get 99.872 Seconds.
-ERD50