- #1
Simpcar
- 6
- 1
Hi everyone!
I'm trying to understand why when writing the differential equation of a discharging RC circuit [itex]V_C-Ri(t)=0 \to q(t)/C - Ri(t)=0[/itex] we replace [itex]i(t)[/itex] with [itex]-\frac{dq(t)}{dt}[/itex].
I read many threads but I don't understand the physics behind this. The usual answers I read are something like "by using the passive sign convention" or "because the current must be positive".
I'd like to solve this problem because it is driving me crazy!
I'm trying to understand why when writing the differential equation of a discharging RC circuit [itex]V_C-Ri(t)=0 \to q(t)/C - Ri(t)=0[/itex] we replace [itex]i(t)[/itex] with [itex]-\frac{dq(t)}{dt}[/itex].
I read many threads but I don't understand the physics behind this. The usual answers I read are something like "by using the passive sign convention" or "because the current must be positive".
I'd like to solve this problem because it is driving me crazy!