Current source and capacitor in parallel

[fredro]

I don't know if this is the right place to post this question, but here goes.

Whilst solving a circuit in class from a homework assignment, we arrived at a situation where a capacitor was in parallel with just a single independent DC current source. The question is, would current flow through the capacitor? The cap was charged (sequential switching situation) to 9.9 [V] beforehand. Many people in the class felt that the capacitor would allow current to flow even with no other circuit elements present. The source is ideal, by the way.

 

[gneill]

An ideal current source in parallel with a capacitor is a one of those situations that's best avoided unless there's something else in the circuitry to limit the duration that the connection is made or bypass the current! The reason is, the current source will continue to force current through the capacitor indefinitely, adding more and more charge to the plates. As a result, the voltage across the plates will continue to rise indefinitely also.

For ideal components the voltage would continue to rise linearly forever. For more realistic components the capacitor would shortly evolve into a ball of plasma and molten plastic and metal flying by your left ear when the manufacturer's stated maximum voltage limit is exceeded by egregious margins

 

[NascentOxygen]

Whilst solving a circuit in class from a homework assignment, we arrived at a situation where a capacitor was in parallel with just a single independent DC current source. The question is, would current flow through the capacitor?

It would. The current through the capacitor would be exactly what came from the DC source. For this reason, I would prefer to say they are in series, rather than parallel. On paper they might be drawn using neatly parallel pictorials, but electrically I'd call it a series connection of a capacitor and a current source.

Oh, BTW, I award you an extra half-mark for using "whilst".

 

[fredro]

It would. The current through the capacitor would be exactly what came from the DC source. For this reason, I would prefer to say they are in series, rather than parallel. On paper they might be drawn using neatly parallel pictorials, but electrically I'd call it a series connection of a capacitor and a current source.

Oh, BTW, I award you an extra half-mark for using "whilst".

I agree. I said parallel because in the circuit, they are in parallel. With the switches in the circuit, there exists a moment of time when they are the only two elements in the circuit.

 

[DeeNos]

I can provide a response to this question. In this situation, the capacitor and current source are in parallel, meaning they are connected to the same two points in the circuit. In this case, the capacitor does not allow current to flow through it, as the current source is an ideal source and can provide a constant current without any other circuit elements present. The capacitor acts as an open circuit in this scenario, as it has reached its maximum charge of 9.9V and cannot hold any more charge. Therefore, no current will flow through the capacitor in this situation. It is important to note that this is assuming ideal conditions and in a real circuit, there may be some small amount of current flow due to imperfections in the components.