Hi mates, I have problems solving the third part of this exercise, I've already done all the previous calculations.
Given the following circuit, where the switch S is open, the power supply = 50 volts and:
- The initial charge in the C capacitor: QC = 0 coulombs
- The initial charge in the 2C capacitor: Q2C = 20^-6 coulombs
- Switch⇒I find the current passing by the amperemeter (IA) and the voltage across the voltmeter VV After a long time t (t>5 time constants). (Done).
- Switch⇒II find the voltage across the voltmeter VV passed 10 milliseconds. (Done).
- Switch⇒III next get the final reading of the voltmeter VV at a given time t (t >0 ∧ t< 5 time constants) and the energy dissipated in the resistors till that instant.
- Ohm's law: R=ΔV/i
- Capacitance: C=q/ΔV
- Kirchoff's laws: Σi=0 ∧ ΣΔV=0
- Energy gived by the battery until an instant t
- Energy dissipated in the resistor until an instant t
- Energy stored in the capacitor until an instant t
The Attempt at a Solution
As stated before, I've done the first and the second parts.
For the first:
Well, here is where i get lost, because I dont't know how to study and analize the circuit formed at this point, I've only seen discharging RC circuits whis a single current, one resistor and one capacitor due those elements could be joined into their equivalent ones, but here, I get 2 resistors, 2 capacitors and 2 meshes, like this one.
I know that the initial charges at this point are:
In order to get the initial charge in the C capacitor I used the voltage obtained in the voltmeter in the second part at the 10 milliseconds, because are connected parallel. So, multiplying that voltage times the capacitance, we get
The initial charge in the 2C capacitor stills equal, since its an ideal capacitor, so is the same: Q2C = 20^-6 coulombs
33333333333333.png19.6 KB · Views: 283
attachment.jpg30.4 KB · Views: 578
Image1.gif621 bytes · Views: 376
Image2.gif666 bytes · Views: 380
Image3.gif624 bytes · Views: 378
58_59e4a5e4c7a317067e0e748d4c7303e8.png1.2 KB · Views: 338
55_39ed5ab39f3e1b932d58b8143acf9655.png1 KB · Views: 342
49_549e15a8fc3c64f775b461c0ce4c83f2.png870 bytes · Views: 332
73_a3a7a2e80e63986351b15fb412bb6203.png981 bytes · Views: 362
34_76bab7f98db551c5bfbe82b73004a907.png1.2 KB · Views: 370
49_f93ffa7bf895f1ac07d8dc5df756a1e0.png1.3 KB · Views: 345
Last edited by a moderator: